No enough info to work with here, but for 3D you want to go up on the diameter and down on the pitch. Try something like a 20 x 6 for your application and you will have much more static thrust for 3D work. More diameter and less pitch also helps to keep the speed down, which can help a lightweight 3D airplane live longer!

I also agree with the APC prop advice, and that's what I use almost exclusively.

Good luck,
AV8TOR