the trick i used to get good chain tension on a fixie conversion is this:
pull the wheel as tightly back as you can into the drops. i then would push the wheel crooked against the chainstays on the non-drive side and tighten that side. i would then push the wheel back into the center of the stays, hold it there, and tighten the drive side. if the wheel was a little crooked still, i would slowly loosen which ever side the wheel was pointing towards and it would then sort of pull the wheel into center, then of course tighten it back up. i absolutely love my chain tensioners for the track ends on my iro. it makes life so much easier.