The one pair of PI shorts I have, the chamois is really bulky. Bought them when I was just coming back to cycling, don't wear them unless everything else is dirty. The chamois could be the problem, if that's the case with yours.

But the saddle is a possibility as well. The Lithia is awfully squishy (I used to ride one), so combining it with a bulky chamois is a recipe for trouble IMO.

There aren't many saddles more T-shaped than the Spec' line, unfortunately for me and possibly for you. Brooks; SI Turbomatic, which is the one I'm probably getting when my Jett wears out; I'm not aware of any others.