thanks!

i went with the second topeak one, for road bikes, for now. if that doesn't fit, i'm going to try the zefal one. both of them are interesting to me because of the no detach when folding. i think the pdw one will be too short. after those, i'd try sks 29" and then the defender. the sks ones seem quicker to release from seatpost in my experience so far.

strange that the defender works for you, but the sks xtradry extends almost the same distance, might be a matter of one inch!