You could try putting the ailerons back into the spin to the right, this helps on recovery by bringing the angle of attack of the two wings closer together again... Most of the time the power needs to be on to recover with a model... I had the engine quit during a flat spin with a model and it was completely unrecoverable... but you may try pulling power back to see what happens... the other technique you could try is rocking it with the elevator (full down-full up- full down-full up) this is what the F-16 does to recover from a spin, or I should say that's what it's computer does.

But to be safe move the cg foreward to the suggested position before attempting the next flat spin... that has the greatest impact of all.

Ty