RE: metal in oil
Hey, just saw your thread, I had a case like that, an old MDS heli engine. Turned out to be a wrist pin circlip that came out and wedged inbetween the piston and cylinder wall, grooved the piston etc. until it finally blew out the exhaust port. It was still running fine, probably would have a while longer too but I was so curious to know what it was I went in for a closer look.
I don't know what type of wristpin keeper supertigre uses, just my thoughts, I'll be watching your post to see how it goes!