Interestingly enough, I would encourage you to consider the exact opposite and put it on top. If I am shooting and need to transition to the red dot all I have to do is lift my head up (I have a giraffe neck which helps). My stock stays in the exact same place on my shoulder, so I am not trying to cant my rifle, especially if shooting supported off a bipod or tripod. Its a better height if using head mounted NV like a PVS-14 if that is applicable/important, and I run my AR-15's the same way. Lastly the windage and elevation adjustments and trajectory of the bullet out of the rifle all remain consistent when viewed through your primary optic. I find overall it just works better for me and less likely to get bumped and damaged as well.