Whew! One thing that may help, if loosening and shifting the chainring doesn't even things out enough, is to take it off and rotate it on the crank spider, then starting the process again. Ultimately, you may have to live with a little extra slack at some points in the crank rotation, and it's hard to avoid with parts intended for multi-speed use. It generally only bothers me when I have the bike on the stand -- it rides great otherwise.