Hi guys, for bench shooting, it is ideal to have a parallel forearm and but section, and let the rifle free recoil. More like the shape of the RAW BM500 stock.
My converted Boss .25 (~900fps/king heavy, ~60ft/lbs) recoils significantly (for a PCP that is) and with the original stock, it likes to be held tight against the shoulder. When I don't, the gun will string vertically.
I mostly shoot the Boss with the Aeron skeleton FT stock, for which I machined an extra alu bar at the butt stock for the rear bag (parallel with the forearm) to let it free recoil in a perfectly linear way.
It is a matter of trying, I've noticed some pcp's are more "hold sensitive" than others. (E.g. HW100, very hold sensitive IMO)
Luckily the Royale/Boss is a smooth shooter, it can be noticed that the hammer is very light, which is important to have less movement when pulling the trigger.