I finally got the Big Dots out to the range.
Result? Nice, normally-sized group, about four inches high. Since I haven't loc-tited the rear down, the wee allen wrench supplied can loosen the setscrews and allow for horizontal adjustment with your own fingers. Knocking the group over two inches was no big deal. I have no idea how i'm going to adjust vertically, since there's no front sight to file down, and the rear is not going anywhere vertically.
Clearly, they aren't an impediment to accuracy, at least at my own level of competence. In fact, they block out a lot less of the target, so they're a lot easier to use.