Well, that kind of depends on if or what back up sight you use. The mount that allows the scope to be mounted furthest back is the #19s. As you can see from the pic, it hangs back some what. This will allow you to mount it the furthest back without a BUIS, or, if you happen to use a #40, #40A2, #40L or Knights 300M BUIS. All the other mounts I am familiar wil are pretty equal in how far back they mount.
I will add, however, that if you feel you need to mount the scope further back, you should probably change your stance to get your eye closer to the scope as opposed to the scope closer to your eye. The only time I have seen people wanting the scope mounted further back is when their stock is too long, or, when they are leaning their head back on the stock instead of forward on the stock. YMMV...