I've tried it as far forward as it will go and as far back as I can mount it.
In my case my Steel Challenge times seemed to improve with it forward. Possibly a fall back on my old iron sight days. Putting it closer to the front sight just seems to help.
FWIW, I found the same thing on my Open Class shotgun. The further forward the red dot the better. (Within reason of course.)
Honestly the the working theory with reflex sights like the fast fire and venom is the further forward the better. Reason being is it gives you a better sight picture with both eyes open same deal with red dot sights like the sparc and strikefire. Tho I don't know if that's true for handguns has well, but seems to me the theory would work the same. Now if your like me and can't seem to ever keep both eyes open bring her on back lol.