F.Alonso,
what tension are you running at the moment?
I've have mine on stock tension, however a) the belts i have are quite old, and b) i'm running 27t stock.
With new belts, I'll run -1 both front and rear.
For mod, you could try going to +1, even +2 clicks on the bulkhead. should stop them flipping.
Regards
Ed