I really don't like in-line blowers in a kitchen fan. They are fine for bathrooms, but kitchen fans deal with grease, and an in-line fan is very difficult to get at and clean, leading to an unsafe grease build-up over time.
Unless you have a grill, you will not need 1200 CFM. If you plan on stir-frying a lot, you might consider a 8-900 CFM unit, otherwise 600 CFM seems about right. By reducing the CFM requirements, you also dramatically reduce the size of the ducting, which saves space and money. Lowering the hood also reduces CFM and duct-size requirements-32" seems to high-most are set at 30". Mine was originally set at 36", and I had to have it lowered to 30" to prevent the smoke alarm going off.
Internal motor installs are less expensive and easier to get service for than external ones. As to noise, remember that moving air is the main source of noise, not the motor/fan. The fan blades do make some noise, but most of the noise comes from the moving air.
The rule of thumb is that each 90 degree bend equals 10 foot of ducting. Most hood installs are designed to have 10-30 foot of ducting.
Lastly, I don't think I've ever seen an outdoor fan installed upside down. Is it possible to do this?
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