I agree with the prior post - a .35 to a .40, or maybe a Sportster .45 will work fine. I have a tuned pipe .40 on mine after beginning with a weak .40 and I like it better but it winds up needing tail weight. Balance it as a floater and you'll enjoy it a lot. Not quite as good a floater as a Kommander, but its nice and looks more modern.

Haven't flown my Kiwi yet, but I like the way the "K" series builds and flys in general. I think there are Kiwi, Komet, Kommander, Kavalier, Kaos, Kadet, and a few more - guess I'll keep finding them around at the auctions.