I think you'll find that it won't help much. The fin and rudder area is still going to be too high compared to the fuselage area. Also the design is more of a speedy racer'ish model and just does not have much side area in the first place. You'd be far better off to admit that this is a design for just cutting some snappy high speed passes and pylon type turns and go for a new model for doing knife edge and similar stunts.

But if you insist on trying then I suggest you add a profile or built up canopy over the wing and have a tail extend back to the fin to add side area higher on the model.