Fred, I probably did put that piston in backwards to keep the ends of the rings away from the damaged port. I did look for an arrow on top of the piston and didn't see one (I've built VW engines and know that the pistons are supposed to be oriented the right way)...
On my last bike (QT50), I mangled the muffler trying to clean it out (which it DIDN'T need) before I discovered how clogged up the exhaust port was.
I've been wrenching for over 20 years now, and I've made lots of mistakes, and tried to learn from all of them. If I offer anyone any advice, it comes from my own experience (and I'm no expert), not from something I've read somewhere. Don't consider it gospel, just an added footnote.