Okay, the disc sounds tricky. I don't suppose you could carefully solder some of the holes up, although I suppose the holes aren't in the same location though, so even if you did solder all but three holes you wouldn't have the pattern the same- which I assume is intentional in the design of the progression feed. Hmmm, tricky work.

Could you drill out the entire progression bypass and replace it with a new section? Sorta risky though.