I posted #2 in a hurry but I agree with the consensus here. If your OEM sight was plumb, your aftermarket should be too. I would shoot it this weekend at maybe 25 yards to confirm what we already know (doubt you'll get it on paper much further than that if your illustration is accurate) then take it back.
“Nine-tenths of tactics are certain, and taught in books: but the irrational tenth is like the kingfisher flashing across the pool, and that is the test of generals. It can only be ensured by instinct, sharpened by thought practicing the stroke so often that at the crisis it is as natural as a reflex.” ~ T. E. Lawrence