Really only you can decide where to mount it based on the shooting situations you will be using the combo on most often, and your shooting style. Whatever magnification you'll shoot it most SB your guide. I would mount it at the highest magnification for your intended use that your abilities will let you use reliably.
I generally mount fixed/variable power scopes for offhand shooting differently than I mount high magnification variable scopes that will mostly be used off a shooting bench or rest. For offhand it SB where the pistol is most comfortable for you to shoot offhand while giving you the complete picture at the magnification you will most often use it at. Shooting off a bench or rest allows you to get the picture a lot easier no matter where mounted or at what magnification, so how it is mounted is not as critical.
The Burris 2-7 is a great do anything mid range scope that is pretty forgiving with eye relief, so you will have a lot of latitude both when mounting and shooting it. I have several of them, and except for my long range barrels with high magnification scopes on them the 2-7 is one of my scopes of choice on many hunting barrels. I shot IHMSA with these scopes for many, many years too, and they are perfect for that. Mine are getting old now and have seen a lot of use, but they have never failed even on my handcannons. Most of mine are the 200293 that I think was discontinued or updated.
IMO-YMMV
