Welcome aboard dlach! I just checked the specs on that bird at Tower. With a 48.75" wingspan and an electric all up weight of 2.7 lbs you have quite a bit of flexibility. Standard radio gear is designed to fit this model, so that shouldn't be an issue. This is the equivalent to a .25 glow model. I would cover it with either regular Monokote or the lighter Econokote but any iron on type covering would work. The old O.S. is sure cool, but they weren't near as easy to use as the newer motors you've got, although it or any of the engines would probably work great. The .42 will surely be super overkill in this model as it would easily power the 60" big brother to this trainer. If it was me, I'd put the .40 surpass on it for the cool factor of the four stroke sound.

Keep us posted which ever direction you plan to go.