I have been scouring here and on the internet trying to figure out if I should buy high or extra high rings for my PTR91. I have a Vortex viper pst 4-16x50 30mm scope that I am trying to mount on my PTR. I also have the B&T universal mount and will be using the Magpul prs stock. Was planning on ordering some Burris XTR rings but not sure if the high or 3/4" will clear the rear sight or not but also want it low as possible. Any help greatly appreciated!