P99 and X300u

I've seen a few posts, here and elsewhere, that briefly mention modding a P99 to accept a Surefire X300, but I haven't been able to figure out exactly what the mod is and if it's advisable. Has anyone here modified either an x300 or the P99 so the two work reliably together? I'd prefer an x300u-A over a TLR-1HL, and the P99 is the only gun I have or ever will have that isn't compatible.