If you want it to fit "directly precise", get a Limbsaver or Pachmayer from your dealer and have it ground to fit. I've never seen a perfect fit out of the box and nothing is uglier, IMHO, than a recoil pad that's not perfect.
I put a Hogue on my Ruger African .375. Its about three times as thick as the oem one. It mitigated the recoil quite a bit. It fit very well - no grinding.