I've been trying to get a rack installed for three weeks now... I have tried multiple collars, and the current one is a 31.8, which is just shy of the seatpost width. Has anyone out there purchased a seatpost collar for the Stromer, or do you know where I might try to call to find out what size collar is required? Or is this some sort of odd-sized seatpost or something designed not to fit any collars because they want you to buy the City Kit???