I just fixed this on my game with Cliffy installed by removing the blue rubber stop. I could probably cover the metal scoop with something softer (but not bouncy!) to protect the balls, but I'll replace them periodically anyway.

My bounce-out percentage now seems to be about 10%. Honestly. I've actually taken down my CL ad to sell the game because I want to see what I can do with the turbo boost hole actually working.

Thanks for the suggestion, but it's working so well that I don't think it could improve.

Yes, but IMHO it's well worth dealing with the turbo boost bounce-outs to protect the playfield. I feel like I'm cheating when I play a game with a scoop hole that's 50% larger than it should be due to edge wear. It's not fun honestly. And repairing that is messy at best.

I think the issue is the tiny bit of bounce that the ball gets from hitting the front lip of the cliffy (worse if the cliffy doesn't stay flush with the playfield). And the stock blue rubber on the scoop is too resilient (maybe after 20 year of oxidation?), so I was seeing literally 80% bounce-outs until I removed it.

My solution was to remove the rubber stop, but there are many others (including the suggestion just above to replace the blue rubber circle with some "dead-stop" foam, which I believe is the stuff you can buy to put behind stand-up targets). Another person had success adding foam to the guide to the left of the turbo boost hole.