can you run the duct work to an outside wall inbetween the joists? the motor you pick (along with the recommended duct size) will result in a "maximum recommended duct length" per the manufac. Also, addding 90 bends to the duct will "add" a variable amount of resistance (equiv. to 10 feet of duct length for my 7" installation). again, you might ask a contractor about running the duct between floor joist in the ceiling, to an exterior wall. you would probably need some drywall work on the ceiling, some messing with the cross members between the joists, but it might be easier than running something up to the roof..depends on your layout

I want to echo Weed's caution about being sure on code compliance when having your vent going out near that window. Last year, when I was doing a re-routed of the vent on my range hood, the local building inspector happened by. (We are on pretty good terms so there was no compliance issue.) I asked him about the rules and got a long dissertation as he handed vent tubing up to me. The gist of it was that the rules for range hood vents are different than for those that directly vent gas appliances (say a water heater power vent). There is some discretion when it comes to venting from a range hood over a gas stove. How far the vent has to be from an opening window also varies with whether the vent is above the opening window, at window level or below window level. I was told the vent that is above an opening window can be closer than one at or below window level. BUT, you want to be sure that, if you open the window while the hood is running, it won't be sucking in the vaporous stuff that was just blown out the vent.

I see a double sink in the angled eating island, far from your other work areas. What if the angled idea is done away with and you make a double wide island instead, placing sink area linear to the most common work area. You have the eating area at one end and the sink at the work area side. This gives more room and maybe you can incorporate a kitchen dining table better? Personally not liking the two islands the way they are placed for sake of flow, and the double wide islands are better for storage, and baking space ie really spreading our for cooling cookies etc, also the shelves below can be open for access at either end which will allow storage space for any oversized platters or cookware. The look would be nicer and more substantial than a 24 inch wide island even if theres 2 of them. I have had a double wide island, with both sides accessing storage clear through, and prefer it to a 24 inch wide anyday. Also while in the planning stages consider 36 inch drawers for pots and pans and plastics etc instead of lower cupboards. Much easier to keep tidy and access things. You wont regret it. I didnt look at the prior list of suggestions, sorry if this is redundant.

54-inches (4.5 ft) x 2 ft = 9 sq. ft. Desired volumetric flow rate to achieve 90 ft/min across the hood aperture is 90 x 9 = 810 CFM. Blower rating needed to pull 810 CFM with decent MUA will be around 1200 CFM, as you noted. Fantech provides 'fan-curve' data in the form of tables, and also plots. A 1200 CFM unit (at zero static pressure) will show a value near 810 CFM at some pressure drop (about 1.2 inches, w.c., for the FKD10XL). Excluding MUA, most pressure drop will be from the hood baffles, unless one has several tens of feet of duct. It would be useful for you to obtain pressure loss vs. flow rate data from Bluestar. Fantech in-line blowers are, I think, axial blowers (like a turbo jet pressure section) rather than a flat plate with radial fins (like turbo chargers use). Broan blowers, including inline, appear to all be the plate type. There is nothing wrong with these, but they may have a different characteristic fan curve shape than Fantech's blowers. I've never plotted both together. (It is important for residential blowers operated at uncontrolled pressure losses and any speed from low to high that they have monotonic fan curves. Else they might 'hunt' at some setting. That would be annoying.) Plate type blowers are least conspicuous built into a roof cap. Commercial up-blast blowers use induction motors often tied to the fan assembly via a belt and sheaves. These can be tailored to provide the desired CFM at lower fan speeds, thereby reducing noise. They are, however, significantly more conspicuous on the roof. The primary advantage to using a hood manufacturer's specified blower is that it will directly adapt to whatever fan speed controls are built into the hood. Other blowers may require some type of adapter or control replacement. So a Blue Star hood's control nature might have to be determined. My Wolf hood adapts to my Wolf blower, made by Broan/NuTone, and likely would work with any other single wire pair induction motor blower up to some motor power limit. The Fantech FKD10XL data sheet show curves for a 5-step transformer control, and for no control. One would have to check with them for compatibility with whatever the Bluestar hood uses, such as phase control. If you use an in-line blower, you also have to find a suitable roof or wall cap. Fantech many sell these. You should have a damper at the hood and also at the roof cap. You need to plan out the entire hood duct path. Is there room for a silencer? Can the duct path rise over its entire length (desirable)? What elbows are needed? Fantech makes some duct couplings that may prove useful. Hanger strap material will be needed. Sound dampening material may or may not be needed depending on blower assembly vibration, which is mostly, I expect, due to blower fan assembly balance quality. Best to match MUA actual flow rate to hood actual flow rate (ex: 810 CFM). This avoids all (well most) pressure drop in the house, conferring safety with combustion appliances and keeping the wall dust in the walls. If active MUA is needed to do this (depends on combustion appliances and their MUA, if any) then a blower that can provide the required CFM at the MUA path pressure loss (usually any air filters, but could include the heating scheme if hydronic). As usual, the duct diameter in the hood exhaust should support a full speed flow rate of 1000 to 2000 ft/min. The otherwise clean MUA path is not grease deposition constrained, but larger will reduce pressure loss if there is room -- useful particularly with passive MUA. I'll skip MUA control in this message, but it needs to be addressed. Commercial rigs usually run at constant speed (exhaust and MUA), so tuning is easy. Residential variable flow rate, along with perhaps a need to deal with other exhaust fans and fireplaces, imposes more difficult conditions for blower control. You might need a Fantech MUA setup, or their 10V control type blowers run by a controller trying to keep house pressure relative to outside within some bound.