Wouldn't that be something you figure out yourself?
FZ2 has added weight to hurt those R2s and give the XR2 a chance by having a possible tire advantage (eventhough the FZ2 might still be faster in Q and race hotlap pace). The FX3 also has 1 less % than normal to give some of those teams at least a fighting chance as long as they run a consistent race (pace shouldn't be within .5 of the other two, but it's consistent enough to compete).
The bit I worry about XR2 is that it has the less fuel start of stint, therefore should be faster than FZ2 by a tenth or two, where then the FZ2 should take that advantage back the second half of the stint. However a simple restriction change most likely won't help that cause, and a weight penalty is all that can happen. 10kg is about 2/3 of a 1% restriction as far as P2W ratio. So it should be close, but you would never know without comparing stint times.
If however you can't get to a 46 at the end of stint, then the XRR might have to be looked at. Of course you would need decent proof, not just "I can't get it down to a 46".