Jack, the Pachmayr Slip on #4 will work on both the PM9 and the P380 and I highly recommend. Other options for increasing the girth of the backstrap and adding additional cushioning is some cut-to-fit Dr. Scholl's mole skin placed under the slip-on grip. As for other slip on grips, Uncle Mikes I believe has a small one that will fit. The Handall Jr. should work fine on the P380, not sure on the PM9. As far as strength, the Pachmayr is the strongest of all and easy to trim if so desired. It's just not that easy to find but our store has them.