I'd agree, running is probably your best bet. I DO NOT like to disturb a piston/liner (disassemble) unless absolutely necessary. I just feel like the fit will never be the same - especially with ringed engines (even if you don't touch the ring). Maybe it's just paranoia, but it kinda goes along with that "if it ain't broke..." reasoning.

I just went though a similar situation with my Saito .50 - it hadn't been run in about 10 years, and compression was weaker than I remember... once I ran it though, all was well.

Do let us know how you make out with your ST...

-Joe