Todd,
Not sure if you have seen the following link but Rick's bike has been lowered with shock settings as well as with addition of a yamalink. The photos show what he sets for chain tension which is a bit different that the Yamaha service bulletin due to the fact that he lowered the bike. Take a peek and then decide where you want to set yours.
http://www.rickramsey.net/WR250Rmaintenance.htm