suggestions for hanging inner "cathedral" ceiling?

I am building a room-within-a room and the (very reasonable) drywall contractor who is hanging 2 layers of 5/8" on my 'outside' wall (with GreenGlue between each layer) only works with steel framing. We are planning on using 16 gauge steel for the joists and studs 24" OC so the interior walls can carry 2 layers of 5/8" (again, with GreenGlue between layers) and still hang (non-structural) things on the walls. I am thinking of using Mason Ind HD & WHD DOUBLE DEFLECTION NEOPRENE HANGERS using steel rod to hang the steel 'ridge beam' from my existing LVL ridge beam and connect my steel joists. The inside room dimensions will be approx. 27' long x 18' wide x 13.5' at high point of cathedral ceiling. Does this make sense? Would I be better off using 2x4 wood for studs/joists from a sound isolation point of view vs. using 16 gauge steel framing? Rods book mentions using steel framing and that light gauge (25) is good from sound isolation but limited by amount of weight can be added to interior walls. Thanks for a wonderful resource.