David, I figured you'd need only a canopy, but your choice of wingspan seems to be 1:4 scale and that would mean you'd need the canopy of the middle-sized model from the German website.

Rusty gave a broad hint, so I'd compare the model plan you're using as a template to the [link=http://www.toni-clark.com/english/modelle/cap21/cap3v.htm]three-view[/link] of the original. From Deadstik's hint I infer that all CAP models are heavy, as you stated above, and I would add "too heavy". I mean it's not "scale" to build the models that heavy and I think that's why they snap so unduly. Even though the original was designed for good snap performance, it has a moderate wing loading - already a bit more than the Z-50, but even a bit less than the Su-26 and far less than an Extra or Edge. The snap behavior is very wing-loading dependent.

As far as I know, the special airfoils above are made to give a predictable stall. The wing should give good lift before stalling and when it stalls it should do it completely. Again as far as I know, the bigger models were designed for the big gas engines available back then. Today's gas engines are very powerful with pipes and just allow all modern maneuvers (including 3D), but they are still heavy. Your intention to build a lightweight model seems to be very advisable to give a more "natural" stall and snap behavior, regardless which type of power is used. I even think that electric is still quite heavy - what is traded off by the big thrust - so glow might be even better for low weight.

As airfoil you could as well use E 169 which is a bit thicker so it would be easier to build a lightweight wing, but maybe that's true only with a built-up wing and a thinner foam wing would be lighter but still strong enough. The airfoil on your plan might be Selig 8035 (hardly distinguishable from NACA 0014), at least it's an aerobatic airfoil and has similar thickness. Just a guess.