I think a glow forum might be a better place for this. For the most part, airframes are airframes; there is very little that differentiates a glow airframe from an electric airframe. Of course you use less material on an electic and more on a glow, but besides that...

Anyway, the power system is what really makes one different from the other, and you're asking specifically about a glow engine in a group primarily focused on electric power. Fine and dandy as long as somebody that flies both pokes around, but a lost cause on a site like The Ezone...

Six cells, direct drive 600 motor... Hmm.. A .25 would overpower the poor little plane and tear the wings off. I'd say a strong .15. This is an old design, so it may not even need to be beefed up to take the banging and shaking from the engine.