The Olight PL-2 doesn't quite fit the p99 rail. Clamping force is ok, but I had to remove the glock insert, to allow it to fit. I have still yet to get a reply to my query for a new, modified top plate (from Olight) for the PL-2 that would permit it to fit either my p99 or p99c.
I believe the PPQ has the same rail (1913 key, not the Glock key) as the P99. If so the olight mini will work. I have the mini on my M1 5" looks good, ergos- I suspect it would look even better on a 4in P99. BTW-It fits my p99c but will not lock with the key.
Sign up for olight alerts and they discount them about every 2 to 3 months