I have a Flamingo, similar gears as a Brompton 3, and changed to double plate with 39 and 48 teeth. Believe me, it's impossible for me to commute with this gears, I have 6km climbing with 19% for 2km, 23% gradient for 1 km and 27% climbing as my gps says, what my legs say is that with the Dahon Speed I can climb, with the Flamingo no, unfortunately. The only good point is that when I come back from work, I don't touch the pedals, only the brakes. The town where I live is worse, to take the kids to school I have a hill of 1,6 km long wich is very hard to climb walking, and worse towing the bike and the kids.