[jyl]

No access to topside of joists, this is on first floor of a three story house.

The space between ceiling and hood, including the threaded rods and the duct elbow, will be roughly 20-24" tall. I haven't exactly figured out how high I'll mount the hood, but a tall person needs to be able to stand under the front edge without hitting their head, since the front edge of the hood will be about 6" further into the kitchen than the front edge of the range below. Ceiling is 108" high, front edge of hood is about 10" tall. That space will be enclosed with some sort of light wood frame and panel thingy, details TBA. Maybe I'll mount some shelves or speakers up there.

Jacks - hmm, I should go see what I can rent. I don't think a typical drywall lift can handle 400 lb? The jack will have to lift to about 70" above floor. It is all stairs to get in the house, so renting a jack that weighs as much as the hood would be tough.