basement finishing with metal studs. soffits?

Mikey, I have some experience with metal framing. Perhaps I can guide you through the start of your project.

I am presently framing for a bathroom in my basement and one of the walls will be under a cold air return, can I screw the metal channel directly to the duct? Is there a code issue there ? how do i frame the soffits? The ones i've done, i built short sections with metal studs, with channel on top and bottom. I've read that this is where metal excels. Should I be using metal studs on the flat, bring them down,snip,bend at 90 back to wall? kind of hard to explain. Would be easyer to draw a picture. Anyway.what do you think?

I'm trying to imagine the wall bisecting a cold air return.You mean a little 6x12 one?
We never used studs for the soffit. Only channel. But i need an idea of how big the soffit is. H W and L.

metal stud framing
One wall runs from the outside wall across the room to the I beam. that wall has the door opening at the out side wall.The last 5' of that wall will have to drop at least 9" to go under the cold air and heat trunk ducts. Can i just fasten a chanel to the duct work? That wall is the back wall to the main room. There is another wall 4'7" behind that wall that extends from the outside wall inward 8'. This room will be a bathroom.There will be a wall at that point that comes across and ties those two walls together. That wall will run under the cold air duct. Do i need to frame around that duct and then attach a chanel? Some of the soffits i built were 8"h x 12"d x 3'-4'L. I have to build one in the center of the room to cover the main trunk ducks that will probably be around 9"h x 4'w x 10-11'L.Then opens up wider by a couple feet or so and goes back another 15' or so.

Here's the deal...no fastening to ducts with screws...prob better to use liquid nail or another adhesive

since drywall spans 9" comfortably all you need is top channel and bottom channel with some channel in between...the drywall will strengthen it

build your left side(9") and your right side(9") 10' foot long hang them. then connect them with some studs on the flat at 2' centers...that should be quite strong