As to the plastic tanks, I've used nothing but since 1990 with only one problem. That was caused by jarring the plane on a bad road and the clunk bounced forward and stuck there. What a surprise when I turned under in the reverse wingover! Had to happen at the nats, too. The plane wasn't hurt as I got it to the grass down over the hill.
I use the Sullivan flex series for all my PA's, both the 65, the 75, and the 61's I used to have. The one in my first crosswinds is now 7 years old and still fine. Yes, you need to do preventive maintainence every winter, but that goes for ANY tank. I'll never go back to metal.
Blessings,
Will