framing partition wall under ductwork

[backdoc]

I've recently started finishing off my basement and I am wanting to put a wall 15' across to enclose hvac/storage area. I have zoned ac and 8'wide of ductwork with no gaps, in the center of the wall I want to build. I've thought about doubling metal studs under the ducts but am unsure if there is some type of bracing to attatch my header to the ductworkor what span the header can be left unbraced with wood. Any suggestions will be appreciated.

[badeyeben]

My idea is, it matters what you are using for wall covering. If you use 1/2 inch plywood on both sides of the 15 foot wall you should not need any more bracing. But if you plan to use drywall to cover the wall, then I would use diagonal let-in bracing on both sides of the wall that goes past the ducting at least 1 stud. Two studs past would be better. I would also tie the wall to the floor joist above it at least every stud.

[backdoc]

Thanks for the info. If using plywood would you just use a 2x4 header?