Cross-drilled rotors obviously have their place, but it is not in street RX-7s and will not improve performance on street vehicles.
"...as long as your stock pad is not overheatting and causing brake fade, you should be able to stop quicker [with solid rotors] than the guy with drilled rotors...Keep in mind that cross-drilled rotors can eat up brake pads." (Anacas, M. Mazda RX-7 Performance Handbook. Pg 46. MBI Publishing 2000.) If you think brake fades is a concern on the street with the four piston calipers then please refer to my racing testimonial. Another issue is that cross drilled rotors are prone to cracking and there is a good chance that they will have a more limited lifespan than solid rotors.