On our Co-Motion, we run an old school Syncros ti post @ 27.2, and a Thudbuster brand shim. Same size you need. Works fine. The Thudbuster shims are the best quality and longest engagement I have found. Several years and a lot of miles with no problems.

I also bought the Problemsolvers but found them not to my liking but honestly did not try them. The length seemed short and not adequate compared to where the frames tubes / welds were are located.

PK