There is a lot more balsa in there than you need for light R/C (compare the structure with other models shown), and the balsa in the kit is most likely way to dense. Our airframes are coming out in the range of 8 to 10 grams; weigh yours and see where it is... I built one of those 30 years ago as a U/C model with a Cox 020 in the nose. It was my 3rd Stuka, and it flew pretty well. Weak point eventually proved to be the gear legs.
If yours is already too heavy, you could rebuild it with lighter balsa, thin out the LE and TE of the wing, thin down the keels and lighten where ever you can. An alternative, if you really like the Stuka, is to try the 'Simple Stuka' on the SFA free plans page: http://www.smallflyingarts.com/Free_...free_plans.htm
This is a simplified Stuka, about the same size, and meant for rubber power. A few modifications (like making the wing carry through the fusleage, and adding control surfaces to the tail outlines) would make a good R/C conversion.
Any of the micro radios would work (RFFS, JMP, Cirrus MJ, etc., with actuators or 1.7 to 2 gram servos) would work. The N-20 geared motors should do a good job...