• It’s only a length of off-the-shelf 1-1/8” aluminium tube, nothing rare that I’m going to wreck.

  • 28.6mm and 25.4mm are common seatpost sizes, so almost 100% a seatpost shim for 28.6mm to 25.4mm exists.

    Also quill adapters are beefy enough and made of a grade of aluminium that won't leave you with a trip to the dentist.