Benjamin rear sight elevation

Yesterday I found a very nice walnut-stocked Benj 397PA to go with my same-model 392. The 392 shot about an inch high at 40 feet with open sights (front blade even with top of rear leaf, target sitting on tip of front blade) even with the sight elevation screw totally removed. So I had to tape the 392 sight spring down tight to the compression tube to get the shot on point of aim. Now my new 397 has the same problem, however, even with the screw removed, and spring sitting flat on sight base, is still 3/4 inch too high. Any ideas how to fix this without messing with front sight (building up somehow)? Guess could cut rear notch a little deeper, but then front sight would not be even when sighting. thanks