Is your stock already cut flat for a pad? If not, certainly don't do it!
I use a slip on at the range and nothing when hunting. I think I have a medium sized one. Couldn't find a marking on it.
I've had 2 limbsavers on bolt guns over the years and they both got sticky after a few years which is a real pita! They sent me replacements and they got sticky so I gave up on them.
