I have the same problem. I have a 73 Comp I bought new, have the Jubilee and TA drivetrain but frankly I need easier gearing. I have read that one might drill and tap the dropout for a small screw which would act as a derailleur stop. The screw could be removed and the dropout returned to Huret compatibility. Any reason this would not work? Would this be a cleaner solution than using a washer?