To be honest the only way I could get it to work for me was to start with about half inch of slack then roll the bike backward a few inches then check the slack again. When it got tight I loosened the nuts and put some more slack in the chain. Eventually I could roll it back without it being tight at any point. I have no idea how much slack I have at any given time.

I know that means my sprocket isn't on perfect but I swear I measured it in ten or 12 places before I tightened it down. I just don't think i can make it an more center. Then I measured it from sprocket to spoke while tightening it. The are all the same I think. The wheel is a coaster so it could be a bit crooked in the frame I suppose, but it spins true. I have no idea but it seems to work now so I'm leaving it the heck alone. I also have two washers as spacers to get the chain away from the frame and that seems to work as well.

I doubt that this would work for anyone else but It seemed to be fine when I got to ride it yesterday.