I think it depends on whether you're planning to use the Saturn (or is it NTS now?) GRP rear tub, or an ali rear tub.
RP1 and RP2 are only fitted if you are going for an ali tub.
Whereas GRP1 and GRP2 are used if you're going for a GRP tub.
I made my the top diagonals follow CP7 (but it might be better to trim CP7 to make it follow the diagonals?)
You can just about see the way I've done here:
https://lh4.googleusercontent.com/-E...0/S5033022.JPG