I would think if you have a stock Rafale model, and try to fly it without canards, the model will be very nose-heavy, if flown per the Rafale CG with canards. The canards will have the effect of moving the aerodynamic center forward, and (hopefully), the CG was located in relation to the aerodynamic center.

Most likely, you will have to move the CG aft some, from the kit's instructions. Of course, then you may run into the new CG being too far aft for the main landing gear placement.

So I'd suggest adding the canards.