Mrs David has got a 25.0mm USE Shockpost on her bike, which is shimmed up to 27.2 with a USE shim.

I've tried it in 2 frames, I've tried 'oversizing' it with 27.4mm shim, I've tried homemade coke can shims and I've tried a selection of QR seat-clamps and it's slipped down on all combinations of the above!

Does anyone have an secret way to get it to stay put?

I've done a search and can't find anything.

Cheers…

DAVE

PS: I don't want to use a bolt-up seat clamp if I can help it.

Somebody suggested to me that Pace Carbon goop was good for adding a bit of adhesion, but I've not verified this myself.

Pace Carbon Shield grease (and other makes) is the dogs danglies for this sort of thing. My post was rock-solid after using it.