Ok, put my ramp back together with the little pin Pat at Stern sent me. My game is now playing pretty smoothly.
So at this point here's what I've done:
1) 2" by just a hair over 1/4" stick on felt, the stuff is holding on extremely well and covers the rivets and hasn't altered the height of the ramp to keep the ball from going up. How long it lasts? Well I don't know yet.
2) Removed factory mylar and added my own. There won't be any way to tell if it's still damaging the playfield with the old piece.
3) Retightened all the upper ramp posts when I was done. This alone allowed me to adjust how the flap met the rest of the ramp and likely made the biggest difference.
The one thing no amount of adjusting will fix though, but I believe the ramp kit Stern is sending out will is the air balls. The ramp is simply too steep. So if you really get a clean shot up it, often the small plastic "guard" is insufficient to stop it from escaping. I'm pretty sure they're including a larger one.