I've got to install some 2'X5' windows in an existing interior non load bearing wall which has steel studs 16" on center starting with cutting out a new hole. The windows will be custom sized when rough openings are done. I've often worked with wood framing but am new to steel. I'm mainly interested in the method to attach both the sill and headers for the rough opening. I believe I can build out the sides by screwing in 2x4's, etc. to the correct dimension. I'm trying to avoid opening up the walls too much as they are 1/2" drywall covered with a painted,tight weave, burlap covering of some type which I won't be able to effectively match or patch up. Plan to cover perimeter with wood trim to finish. I'm intending to sawzall out a rough opening as tight as possible to start and am considering sistering in 2X4's on the studs, then attaching the sill and header to that. Is there a more appropiate method for this? I'm thinking I'll need some solid support top and bottom for a 5ft. wide window. Any help will be very appreciated.