Kryptonite Flex frame bracket slides around a lot I had my Krytonite mini for a few years now, and I remember installing the Flex-frame bracket on a bike frame which I left outside when I got it. I had a go at removing it recently and put it on my Mint MTB frame and now I'm very unsatisfied with how it slides from side to side when standing and generally backwards.

It seems the rubber running inside the strap has perished and no longer keeps any kind of grip. Would I be able to go to a hardware store and get a piece of rubber that will really keep it in the same place? Do these things actually work with performance oriented riding?
I am going to conclude that this design is poor, is overcomplicated, it only has a flimsy piece of rubber for a strap which doesn't meet with the other elements (namely, the nylon strap and the metal fastener which sit around it) properly in order to achieve a consistent grip, and the rubber doesn't last long. The rubber leaves marks all over the frame as well. I can invent a solution myself that will work better than this Kryptonite thing, which imo only suits bikes that you aren't worried about scratching and aren't going to ride too hard. Any solution needs to mount to at least two tubes on the bike to ensure the lock is held with sufficient rigidity.

The rubber will perish inevitably after a few months outside and then it will be useless, and even before then it still didn't work entirely satisfactorily for when you ride the bike hard up a hill, where it will nudge slightly out of whack, sometimes knocking the knees.