It's personal preference on where you like the optic with a red dot, but there are things to consider. The biggest is not just the optic and where the "dot" is but being situationally aware of what is going on around you and the targeted animal. Having the optic mounted further forward will allow your eyes (yes eyes, because both eyes will be open) to focus on the entire picture instead of being "zoned in" with the optic very close to your face.
With the optic close to you, the edges are more well defined and it forces your brain to "see" them. Move it further forward and they become blurry because you are focusing on the dot. The brain will dismiss the edges of the optic and all you will see is the dot.
This method is not only used in hunting (like driven game in Europe) but has been confirmed with military units and police where being aware of what's going on is truly life and death.
I know that most are not likely to be breaching doors or taking down an active shooter, but hunting DG isn't that far off either. If it were me, I'd look at a way to keep the optic low and move it to the forward end of the action. Another option (depending on the rifle) is replacing the rear sight with a mount for a red dot.
Is the 416RIGBY you are looking at a rifle produced by Rigby? Some pictures would be nice so we can all dream and drool.