I've adjusted my trigger as well, i got my info from the How To Shoot Beyond Belief video. I knocked it down to about 3 pounds, and there is still some adjustment left. One thing the video said about reducing the trigger pull was that besides slam firing it may also freeze up in colder temperatures. I'm not sure how true it is, but they seem to know their stuff. They also suggested using clear fingernail polish for sealing the screw after adjusting it (which has worked well for me so far)
As for how light it goes i think i took mine down to under a pound but when you get that low you have to consider slam fires and functionality of the trigger.