I took my Hayward Ecostar ( same wet end as Tristar ) apart yesterday to replace the shaft seal, I ordered a new O-ring / gasket for the Seal plate - just in case. The O-ring was loose and wouldn't stay in place, I put on a heavy coat of Jacks 327 and stuck it in place on the seal plate. I carefully brought the motor/seal/impeller/diffuser plate back to the strainer body and as I slowly tightened the bolts (a little bit on one bolt, then the same on the opposite bolt then the next two bolt opposite each other etc.) the gasket slipped right in. Yay!