Dont have it on the 45-70, but I do on the 38-55TM, the std from factory simple peep WGRS(?) and once it is sighted in for the optimum distance with the load Im using I dont need to tweak it.
I do like the looks/function of the NODAK peeper, and have proven on the target range that I dont need the big outside dia. target aperture as I shoot both eyes open and dont want to block the field of view for a hunting gun.
BTW, if you want a smaller dia. than the BSA type c/w adjustable aperture the Merit 'field' model is dandy; it adjusts like a camera lens. It is pricey and the much cheaper Williams 'shotgun aperture' is very effective as an all-rounder.