As always with really off the wall ideas like this you can learn a lot from doing what you're planning in a smaller scale. Make up a test glider from foam for the fuselage and simple flat sheet for the surfaces. 1 inch blue foam for the fuselage cut and sanded to the approximate profile and taper and 1/16 sheet for all the surfaces and a wingspan of 18 to 20 inches.

If you can't make it fly in a stable manner as a glider it won't do any better with an engine and radio. The CG will likely be at or just in front of the "trailing edge" of the rear wing.

You can try those strakes but I'm not sure that they'll be effective enough.