Trevor's point is well taken and sounds like he's got great suggestions for much improved ventilation at modest extra cost. But...to restate, a liner that is narrower than the range, and only 15'' deep is way short of adequate. Trevor and ya think point out that the hood surround itself can function as the actual capture area, with the liner acting more as the conduit out for the smoke. That's only partially true. First, realize that the vertical walls of the hood liner will create "dead spaces" inside the hood surround but outside the walls of the liner. For these areas to be vented out, smoke would have to be drawn first downwards to clear the bottom of the liner, then back up through the duct. Since smoke etc naturally want to rise, that's asking a lot and I think you'll find stagnant air and fumes in those areas. More importantly, the area inside the surround not covered by the liner will have no baffles or filters to collect grease. The result is over time there will be a truly yucky buildup of grease and nastiness in the areas of the hood surround not covered by the liner. These will be next to impossible to reach to clean, and if it's a wood liner, it will never come fully clean anyway. Bleah! I'll say it again: if you are going to do a custom hood surround, far and away the best option is to get a custom hood liner that will fit as close to flush with the surround as is possible. I'd also insist on a surround that is at least 24'' deep, as 15'' is just too shallow to be effective. Several companies dedicated to hood production can do exactly that, it's what we did with Modern Aire and is I think the optimal solution.

Depth is also a concern there. I would recommend the Best CP37I482 at minimum or a CP57IQT52SB. Those are 22.5" deep inserts which has a ton more coverage area. Worst case there is also a PK2245 which is the same, but around 43" wide (i can't recall exact width but its in that neighborhood). Ventahood is another quality option. BH346PSLDSS or the larger 352 model. You can also step up to the BH4 which has a little more power.

I think you will be fine with a 24" depth hood. If you did a poll on this forum, you'd find only a handful of people with a hood of 27" depth. They're less commonplace to find and expensive. Your budget isn't that big. I think you are very mistaken about the width of the hood. You won't bang your head on it more cause it's 42" instead of 36" wide. And, without cabinets on either side, aesthetically it will look skimpy to have a 36" hood over a 36" range. I am surprised at your KD, and am questioning his knowledge. Somewhere there is a thread on this topic of hood width aesthetics, and I will try to find it for you. Bottom line, get a 42" wide by 24" deep hood, installed 30"-36" above the range, and you will be happy with these dimensions. I would spend more time thinking about the ductwork. Why didn't you mention it. It needs to be 8" or 10" diameter. If not, that will constrain your exhaust capabilities far more than whether the hood is 27" deep. ETA: I searched Gardenweb threads, but anything on this subject was missing the photos due to Photobucket's new rules making you upgrade (curse you Photobucket) Also check out Costco for hoods. Make sure they have baffle filters. Some great deals on Costco, though the hoods come and go, and if you don't find something check back in a week or two.

There are many people here who can comment on the math. My HVAC person did that and installed MUA. Because of our cathedral ceiling and the hood being at the low point, the hood will have to have an internal blower. (Trust me, we tried.). The Wolf representative pointed out that you need enough CFMs to work if everything is at full power, but if you don’t need full power that much, the higher CFM fan allows you to run at a lower, quieter speed (variable speed blower) for a lot of everyday cooking for 2 people. They make a 900 CFM blower, which is what we went with for a 36” rangetop with a griddle (40”hoodliner in 43” cabinet).