Yep. Building out the side plate will likely resolve the problem. So will an arrow with more spine. Taking off 50 grains just isn't enough.
Another thing that could explain part and maybe all of the arrows impacting to the right is that you haven't adjusted your bow arm hold. If you don't move your bow arm a little to the left with the cut to center bow, you in effect are pointing the arrow more to the right before the shot, vis-a-vis a bow not cut to center. Usually, the brain makes this adjustment after a few arrows, but not always. That's one of the reasons some folks have difficulty switching back and forth from longbows (not cut to center) and recurves (cut to center or past center). Try this. When you draw the bow, and think you are on target, look down the arrow to see where it's pointing. If it's pointing to the right of the intended target, you need to move your bow arm to the left to bring it in line. Consciously doing this a few times should train your mind to bring you back on target. Of course, as others have said, building out the side plate will accomplish the same thing and you won't need to make the mental adjustment. Good luck.