need help, son has savage 110BA 338 lapua with 20 moa rail, and has ordered nightforce nxs 8x32 x56. we had a vortex 30mm scope on there with burris rings and inserts but could not stop the scope from moving. we have a chance to get some vortex rings, our plan is get three rings. what height will I need, med is 1 " to ctr of scope, high is 1 1/8"