Mark,
I have been running an OS 120AX on an OMP Katana 70 V2. It has terrific power, of course. But what I like best is the smooth consistent transition. I just competed a scratch built of my own design for this engine. Its a profile with 1000 aq in of wing and weighs just over 6 lbs. It should be a rocket. I run a 17-6 APC and it turns it great. The light wood props mentioned above would be better. I found I instantly trusted this engine down on the deck, which is what is needed for 3D. As you break in the motor, take care to be sure the low end isn't too rich. Many problems with transition in 2 strokes come from this. I think you'll find this is a great running motor and a smart 3D investment.
Regards,
Dave