After seeing that picture of the fractured seat-stay on the prior iteration of the aluminum frame, I haven't done any experimenting to see how loose I can keep the seatpost (in order to speed up the folding) but have always kept the seat-QRs very tight. The bike rides stiffly with no discernible wiggle. If it weren't for people in town always hollering to me "Is that one of those folding bikes?" I could even manage to forget it was one.

Regards
T