Is there a particular reason you want to build him a little plane? The only reason I ask is that there is not a lot of cost difference in putting together a smaller plane vs. a 40 size trainer kit. The only real money savings will be in the amount of fuel that you use. The difference in cost between an LA15 and an LA46 is only a few bucks, same with the Eaglet kit vs. the Eagle II kit. The radio gear will cost the same, or be cheaper for the .40 size if you plan on using mini or micro servos in the Eaglet. There will be more covering, but that is about it.

Don't get me wrong, I think that building the Eaglet would be an awesome project for you and your son, and he will love learning to fly on it. I was just wondering if you are building a small plane for him just because he is a small guy. It might actually be easier for him to fly a bigger plane.

Whatever you do, please post some pictures. I'd love to see the little guy with his new plane.

Good luck.