1. If the Level 7 was not leaking down the power tube, put that back in for now.
2. Does the RT Classic have one or two tiny vent holes on
Don't use shims. Always use the same o-ring, that's what you're tuning. Follow the instructions in this post here to tune.
You should check
I've been in the same boat for years (ever since my school was the 4th or 5th school to get it) and then my dog made a Houdini escape and I couldn't find