Many folding bikes have large diameter seatposts, including my R&M Birdy.
Do any of you know of a seatpost mounted rack that fits such a large seatpost? I've been looking around, but all the racks I've seen so far only go up to a 32mm seatpost.
(And yes, I do know there is a R&M rack made for the Birdy. But it costs $150, which I think is frankly ridiculous!)