I have a 40' X 54' X 14' quosnset. Biggest/best thing I could afford, and happy about the design - (windload - 155mph - no sharp corners where wind can rip them apart). Pretty happy with it, but I agree you need lots of lights. You give up a little floorspace with the low sidewalls, but I use that for storage. I built a 40' X 12' "loft" at one endwall (other endwall is 12' sliding door). I use 1 12 X 12 X 8' area as a tool-crib for storing large tools (cherry picker, sandblaster, welders, shopvac...) and it also has shelving for hand tools (drills, sawzall, etc. - things I don't use all the time.) The space above is for all the household **** you accumulate. I've got 3 cars in it, putting in a 24' X 12' spray booth (I fool around with old cars too) and it will provide ore storage above the booth. In FL - its not heating... its cooling! I've got a big exhause fan mounted at the top of the endwall and a big squirrell cage fan for circulation wherever I'm working.
I like mine pretty well, but If I had to do it again, I'd put another quanset up - here in FLA, but put on top of 4'-6' sidewalls - giving me all of the floorspace, ,more room for lift and keep the shape.
49T&C