I've got one on my Hemlock until I get around to buying a post in teh corect size. THe first few uses it stayed put, but then the bike sat unused and unwashed for a couple of weeks after riding in seriously shitty weather and on Sat teh shim lifted with the post, slid back into place easily enough though.
I did consider putting a drop of locking compound between it and the frame but wussed out and slapped loads of grease in instead! 🙄
Think i'll see if I can flare the top a wee bit more so it sits under the collar and gets held in place that way.
You may as well give it a punt if you have teh post alrady as it's only a couple of quid. Think I got a brand x one from crc.