Luc, I don't think I like the idea of plastic hanging down.
The tank is going to take up about 75% of the room, so elbow room will be minimal once all the filters are in. The lights are just going to be shop lights with daylight bulbs in them. Not much heat there. My friend's tanks are lit with very little light. They look great and you can see all the fish very well.
It's going to be some trial and error.
I've designed some of the filtration. Tomorrow, I'll take some pics of the water containers that I'm going to make into huge canister filters.
I have a bunch of ideas for filtering the tank. I'm not going to go with one or two huge filters, but moreso with a variety of filters with specific purposes.
Clarity, nitrate control, redundancy, and ease of maintenance are primary concerns. Biological, chemical, and mechanical types of filtration will be used.