You're making a bigger deal out of this than you need to. Just rering the sucker. It'll cost you about $150.
From my experience, unless you are testing with either a snap-on or Craftsman compression guage your readings are suspect anyway. I would feature to guess that your compression is actually higher than the 90 reading you are getting but after 50 hours of running its time to re-ring anyway. Do it before the piston is ruined and you have to buy a piston as well. Or worse the cylinder walls get scored.
Just my humble opinion.