It's funny that you ask that.
I have recently rediscovered the benefits of resurrecting some of my smaller planes and was looking at my UCD a couple of weeks ago and trying to decide if I could be bothered fixing the covering (It is VERY tired and a lot of the trim has fallen off it) I then got to thinking about making it a Gasser.

Bearing in mind that the plane flies 3d very well on a Saito 1.25 and is reasonably acceptable on a Saito 1.00 I think that a decent 20cc would be good on it. The DLE 20 would be a very good choice as it would fit pretty much straight in. Some of the weaker 26cc's would also work well but they tend to be a bit heavy and bulky. By using a smaller fuel tank, Using an IBEC and locating the ignition a little way back, the weights should be fine and the CofG should also be far enough back to 3d well.

I have a spare Evolution/Mvvs 26cc Gasser that I may install just for kicks but I can't use an IBEC on that as it requires more battery power for the ignition. It may be a bit heavy and it may be a bit much power for it but there is always a throttle I can use.