On the how it will look, the different sizes should be okay. Add an inch or two of framing between them if need be and it will look great. The Gaggenau design for the combi-steam and plain ovens is that the controls on the bottom of the combi-steam oven line up with the controls on the top of the single convection oven, and form a square. They'd look REALLY weird side by side, or even in different parts of the kitchen. I resented having six inches of trim on the combi, and tried every kind of design and gave up. I love the Gaggenau ovens, but they're like Apple computers--great but you have to do it their way. Sorry. Still excitable about it I guess... But with the Miele units, they won't look unbalanced next to each other. You might also consider putting them at different locations in the kitchen. People talk about wishing the steam oven was nearer their sinks, so you might want to put yours where it's only steps away, and then the convection oven nearer your baking things. Malhgold--Great picture!! Sigh. I love that arrangement. It's actually not that different from what my oven stack will look like, but mine won't be nearly so pretty...

A custom duct cover is probably less expensive than getting an island hood to solve your problem. (The "chimney" on the hood is really a cover for a duct that the air flows through.) Because an island hood has to be finished on all 4 sides and has to support its weight from the ceiling, it normally costs more than a wall hood which normally has 3 finished sides and is supported from the wall. About the smallest price difference I've seen between the wall and island models of the same hood was $500 and it can be over $1000. The custom duct cover for our hood cost about $500. That was to get a duct cover made with trapezoidal sides because there was a sistered joist in the way of where we wanted to hang our island hood. Since it was for an island hood, that was for something strong enough to support the hood. That is a lot more weird request then getting a "flange" on a wall duct cover. A wall duct cover usually has 3 sides with just flanges at the back for screws. So what you want might be more like a small step or notch in the sides of the duct cover so that the sides are 1/4 inch deeper above the backsplash. I'd expect that to add much less than $500 to the duct cover cost. To ensure that you get exactly what you want, you should draw up a sketch with dimensions showing it. Independent, who made our duct cover, required a sketch from us before they would quote. There might be some practical problems with an island hood against a wall. If it is installed tight to the wall (so that its rear edge touches the backsplash, there might be noise from vibration since it won't be screwed to the wall like a wall hood would. If it isn't tight to the wall, it might be difficult to clean behind and some grease and steam laden air might flow behind it. If your backsplash goes behind the hood, screws will need to go through it that attach the hood to the wall.

I like your idea. It's a minor variation on the one I went with. First off, a simple cooktop set into a solid sweep of horizontal counter gains you a whole bunch of visual organization and a very nice simplicity. Drawer stacks with drawers of one finish sweeping along in matched horizontal lines below that continue the organization and simplicity--regardless of the width of the drawers. I think it'd be kind of hard to goof this up enough to look bad. Now, an oven does interrupt those under-counter lines, but well placed it will all still look good. If it's under the stovetop, appearing to be centered under the vent above the stove is far more important than what size it is. Fact is, a cooktop set into the counter simply isn't the driving feature a range is because it's not very visible. If you're using a look-at-me vent hood above it, that is what will focus attention. As me how I know. :) We also have an L counter with stove and sink on it, and a work island. I designed a pleasant look-at-me wood hood, 42" wide, which with its display shelf is the feature that grabs attention when one looks into the kitchen. To fit everything in on our L counter, we put a 30" drawer stack under the 36" cooktop. Does this look weird? No. When the topic's come up, most people hadn't noticed at all, some hadn't noticed before they finally did and commented on it. BTW, I offset our oven to the side, where the island mostly blocks it from sight on first entering the kitchen. I thought it would look nicer to have the drawers one does see on the right end continue on across under the stove, which it does, and I thought I'd prefer not to have to stand in front of a hot oven to work or to block someone else's access unnecessarily, which I do. Of course, for those who might have cared (not me), the oven's contrast with the cabinets surrounding it would have drawn some attention to the fact that it's narrower than the cooktop above it in a way that the rows of white drawer fronts don't. Not that I wouldn't have placed it there for that reason. This sort of thing may be less common, but as long as the entire construct is visually balanced it'll make visual sense. What would look odd would be if there were an obvious dysfunction involved. Discarding all the usual options for one that just can't work well does look odd and never comes off. Everyone who cooks notices--big time. Like doing without an oven and instead mounting a TV under the cooktop where no one could see it. That would look odd.

Kim: You are at the right place(s). The Appliance forum is one important place for you, but the Kitchen forum is equally important. You need to spend weeks (I spent a few months before my reno design firmed up) reading questions and answers on the many topics that are relevant to kitchen design before starting to flesh out your design. Questions that aren't answered in any searched results should be asked. After a while, you will develop a sense of what is important to kitchen design, and particularly to your kitchen design. Get familiar with grid paper, draw and cut out plan view appliances and counters to scale, draw the room boundaries to scale on a clean sheet, and then move stuff about on paper with a view to aesthetics, performance, and particularly kitchen efficiency. Many here will help you. And occasionally, reread this thread. Gas stoves/cooktops have safety considerations that are more stringent than induction cooktops. Reading the International Building Code or one of its derivatives (Residential Code, Mechanical Code, etc.) on topics of relevancy may help. Or download and read the installation guides for any candidate appliances. You will have to do this anyway once you are getting close to countertop and cabinet design, not to mention plumbing and electrical design. You will need a kitchen designer that can support with a design tool whatever cabinet line you find preferable. Eventually, everything needs to be specified to a fraction of an inch, with cumulative errors (and non parallel walls) corrected by filler strips cut to size on site. In your spare time, decide how you will live while the kitchen is being ripped up and replaced. Rental across the street? Hotel in Pago Pago? In the house with the microwave oven temporarily in some other room? Dust blocking? I had my new induction cooktop sitting on supports on a table in my Family room with an electrical cable snaking across the floor to a nearby breaker box. In my view, once the appliance selections are firm, appliances should be acquired so that there is no issue with unavailability or with the true overall dimensions and placement of electrical/gas/whatever interfaces. These appliances will need to be stored somewhere accessible. Ditto the cabinets. "Measure twice, cut once" is optimistic, as will be most people you will have to deal with.