Some of the new gas engines that have just come out of China are very cheap even compared to a glow engine. The smallest gasser I have is a 1.40 RCS [not cheap] but it's still a 22cc high performance engine and if the weight wasn't a problem then the added horse power could be, vibration could also factor in. Maybe not a good idea for a trainer but I have seen the RCS 1.40 used on the CG 60 size Extra. Still a lot of over kill!!