Just one question in relation to the ceilings, If I had an 8ft ceiling and it was painted in a non reflective paint of the same colour as the rear wall, would this show up in photos? Im thinking the rear wall would be something like 5-6ft behind the subject . . . just a thought . . .
You could cyc the ceiling and floor to the back wall to create an infinity background.
The main reason we're talking about ceiling height here is to make room for modifiers. Having it in the pic will have more to do with lens field of view and angle. It does reinforce the benefits of higher ceilings making arms raised over heads less problematic.

