Why stop there, A.J? Every one of the Kadet line of planes are good to learn with. It's just a matter of how big you want to go and how many channels you want to play with. Since Samuel already has a 40, either the LT-40 or the Mark II would be a viable option for his engine. The big differences between the two are that the LT-40 is an easier build since you don't have to carve anything like the Mark II requires but, at the same time, it costs about twice as much. Here is a link to the Sig website homepage and pictures of both planes:
Main Menu SIG Mfg. Co., Inc.