Does it seem that the raised rail provided by the scope throws off your cheek weld for a scope?
I have a particualrly difficult time with my NSN + jpoint combination with my SIR. The Jpoint seems too high - my chin is on the stock and does not seem comfortable - no problem when NSN + jpoint combination is on the flattop itself?
The ACOG/SIR combo has always been the worst combination of the SIR/Optic settups out there.
Some have no problem w/ combo. others like myself do not faveor it though I can use it.
However, the sight is a lot higher than that when in the carrying ahndle and many use it that way w/ success so it's a personal thing.