@Joseph_1970 Got the PL2 and mounted it this morning…
While I have the M2R PRO Warrior like yours, I do not have a mount, so I laid it on the table next to it so you can get an idea of size (not exact as the barrel in some of the photos is a few inches above the table). The barrel is 9" plus an A2 birdcage, the handguard is 8" M-LOK.
I took this pic as if I was looking through the MRO red dot, and its kinda close. The MRO mount is lower 1/3 cowitness, and I can just barely see the top of the light. I only notice it when I look for it. If you have a full co-witness or lower mount you may see more of it in your window. The red dot is turned off, the thing that looks like a dot in the image is a reflection of some sort that I dont see with my eyes.
A couple notes. I know i will probably never use the BUIS for real and this is a HD/CQB, but… I kinda dont like the front post so far back, that is a really short sight radius. It makes me want to go back and start looking at regular scout-type mounts and a pressure pad. Modlite has a really neat modbutton pressure pad (more like pressure button), but that takes me back into the size/weight class of a regular rifle light. I have kinda decided on a pistol light specifically because I want less size/weight on this rifle, so I am likely to keep this setup, but for others… YMMV.
I do not get any shadow from the barrel, not sure if your flashcan extends a bit further out it may cast a little shadow. The light is mounted on the furthest forward picatinny slot. I am noodling how I might mount it at another position (3, 6, 9 oclock) but a) it would add more weight with an MLOK/PIC mount, and b) I think it would make activation more awkward.
For me, the switch is easy to reach from either left or right side. Activation is intuitive with click for constant and press for momentary. Making it strobe is a “press both toggles at once”… good luck with that 
I picked this PL-2 Valkyrie for a couple reasons.
- I like Olight
- Only 4.06oz
- 1200 lumens, it is more “floody” than “throwy”
- uses 2 CR123a batteries. They offer a rechargable versions in the PL-MINI 2 Valkyrie (600lumens) and the PL-Pro Valkyrie (1500lumens), but I specifically wanted non-rechargeable and just replace the battery once a year. If you use lights a lot, one of the rechargeables may be a better choice. The mini in particular is really tiny and lightweight (2.5oz).
- On sale last week was $75
I see a lot of people running surefire x300 in this same role on AR pistols. There are likely some other models of pistol lights that would also work well in this role.