RE: plane for an OS 50 SX!!!!
Yea, any of the 40 size 3D planes, you want to put a 50 on.
Flip 3D
Hype 3D
UCD
Any of the profiles, those fly well on a 45 and a 50 makes them rockets.
If you are looking for a SA plane, a 50 may be to light, most of them fly good with a 61 however none of them really any good for 3D.