The constant chord (non tapering) symetrical wings found on Ultra Stiks are also almost impossible to snap roll unless you get the CG way back and have a lot of elevator throw. You can most likely re-engineer an Ultra Stik into a reasonable trainer by adding dihedral to the wing, moving the CG more forward, and reducing the recommended control throws.

I also have a Pocket Rocket with a cambered (flat bottom) wing that has a bit of taper and it will snap roll just like tapered symetrical airfoils do. This plane also has dihedral since it is a two channel rudder and elevator plane. No throttle, you just wait untill the Cox .020 TD runs out of fuel to land.