For the 60-size planes, the 91 FX will be a good powerplant for hovering/3D.

Edgeguy: The Saito 180 is a good engine for 3D'ing the 120-size Yellows.... an OS 1.6 will work as well... We've tried the Saito 150, and while it's a great running engine, it doesn't have the extra umph the plane requires for pulling out of hovers with authority... and the YS 140 would be a better match... a 120 is questionable (although I've never flown one, or seen one fly with a YS 120).

-Juhan

ps: You can see our Yellows fly with Saito 180s and 91s on the website listed below... the Saito 91s will not hover the 60-size planes.