Just create another chat tab and set it up for PM's only. That will help out considerably and it won't "fall off" (unless you get the same amount of PM's as chat takes place on 200
). I was quite happy to have the ability to do stuff like that. I have a second tab setup that I labeled as "System", which has all System Messages and PM's, for the rare times I get em.
EDIT: Bah! Lusche beat me to it.