This butt plate would not have a spot for a monopod.
This is only for the back of the buttstock by Magpul and specially for their PRS Gen2 model, not sure it'll fit the Gen3. I have 2 on 2 of mine, 1 on a chassis build and 1 on a PRS AR build. The Magpul PRS Gen2 stock these go on do have a small spot for a monopod if remove the bag rider part, under it is like 3.5" of 1913 rail. I put a B&T Monopod on my PRS AR 1 but not my PRS Bolt action chassis as it's on a Cadex Defense Fiel Strike Competition chassis and I use bags only with it on rear. I wish there was a way to make the monopod sturdier too when extended over 2" out like a spiked foot abd better or another tension screw.