I have shot the flat knocks with my Horton team realtree 175 and they shot just as good as the half moons. no differce at all.
Although it's not what I have right now (cause they aren't handy where I live)I actually prefered the flat.
When using the moons, I always give the arrow a little twist after loading just to make sure that the knock is seated good. Don't know if that's needed or not, but no need for that with the flats.