@FIN13: As much as I support 3R (reduce, re-use, and recycle), I'm not sure it makes sense in this case. If you stick with 200QX motors, mounting with single giant nut is suboptimal. Same with prop mounting, which won't take generic 3" props without a hack (also suboptimal).
If you want a 3" frame, I think you'd be better off starting from scratch with new electronics. 20x20mm electronics are cheap as chips from BG now. Same for 1104/1105 motors, which I think are better for a lightweight 3" build than 1306 (motor size on 200QX). Might as well do it right, with properly matched components.