If it helps, I’ve commuted for years on a Raleigh Twenty, which is practically the same size and I added a big, sprung Brooks B67 (on a 400mm kalloy post) to give another inch or so to the seat and I’m 5’10”/5’11”. It’s probably more height-flexible for different folks, being a sit-up style bike.
Hi - interested for a mate, could you let me know range of effective rider-sizing? I have no familiarity whatsoever with folders! Cheers