My top speed on my Dahon Speed D7 was 28.5mph. It felt perfectly stable although I did not. It seemed insanely fast, car speed minus the car, seatbelt, airbags, etc. Life affirming if you don't die though. Weirdly enough I hit 20 or 21 most days on a nice flat smooth stetch by a scenic lake nearby and think nothing of it at all, I would readily go faster if I didn't have to turn off - on a longer stright I'd go for 25mph under my own steam on the flat and not care one jot. Funny how those few mph and shooting down a hill with street furniture and traffic changed
everything.
It really was 'brown trousers time' that day