Re: What bipod height for prone?
My recommendation is the 9-13. I have one and it pretty much just stays at 9. I shoot it prone at that setting and off a bench at that setting.
You probably don't go wrong with either the 6-9 or the 9-13, but I will tell you thing....be sure to get the notched legs and it should swivel.
The notched legs will lock the legs in position when they are extended. This is an issue if your rifle has sufficient recoil to lift the bipod some. With the smooth legs you have a much great chance that the legs will slip.
The swivel will allow you to adjust the cant of the rifle for ground or a bench that is not level. Once you have it level, a pod-lock is a nice accessory but not necessary.
My my $.02
I'm not gonna shoot here. I'm gonna shoot waaaaaaaay over there!