Already have a PBSF mounted on my seat post. Wanted to add one to a seat stay, but having trouble on my Madone 4.5. The cross-section of the stay is rectangular, not round. Neither of the included brackets will work.

I thought about using the seatpost bracket and using something as a filler (like rubber tubing). Anyone tried this? If so, what did you use as a filler? Is there a different (better) solution?

Thanks!

Tony