It seems like I hear a lot of talk about the thickness of walls and it seem to me that it is overkill. Do the walls really need to be that thick? They just need to be rigid, they are not load bearing.
I was thinking that if you built a frame (like the following)
from 3/4" x 3/4" and filled the spaces with rigid insulation (that pink stuff has a minumum thickness of 3/4") and sandwiched it between 2 pieces of 1/8" plywood, you would get a very rigid wall which was only 1" thick, and quite light. Does this seem right to you?