Something like this?
Can't say about that. The one I actually use was a motor vehicle license plate.
Interesting. How is that working for you?
I can't say I've had any issues with slipping. I am running quite a high post, and I am not particularly light (85kg). I have the bolt torqued to just over 2NM
I've marked it with crayon to pick up any slippage.
However, my seatpost is painted. Almost wondering if that thin layer of paint is enough to put the post within tolerance. Seems like slipping occurs more often than not
Is it painted down to the insert area?
At one time, I've tried wrapping the seatpost with some tapes to increase the cross-section, but it didn't work.
My current method worked for me. No more slippage and no damages to any part. Previously without the plate, the bottom edges of the wedge scratch the seatpost when the seatpost slipped.