I have a Trek and a Downtube folder and like them both a lot! This morning I had some radio work to be done on my small homebuilt airplane (Kitfox) at our local airport and as I fly from a small grass strip about 10 miles out, I folded up the Trek, flew in to the big airport, and rode it back out! I'm sure the downtube would have folded equally well - I just took the Trek cause it was closest to the door.
There's no significant baggage compartment in a Kitfox, so folded it and bungeed it in the right hand seat along with the seatbelt to make sure it didn't flop around and hinder the controls. Worked great, although I would recommend anyone doing this to tie it down securely so it doesn't come loose at an inopportune time.
Normally with my bad back I ride a LWB recumbent! After riding the diamond folder my butt and back feels like it has been kicked by a mule.
Anyone know of any SWB folder bents, other than Bike Friday? I have a Raliegh 20 I've been thinking of trying to turn into a folder bent.
No other commercial quick-folding two-wheeled bent other than a Phaser, and even then I've heard the fold is not quick. (I've seen many solutions from outside the US, though, including kits for Bromptons and Birdys which are probably no longer sold.)
But if you're going to build your own bent, might as well make a disassembling Monty.
Edit: There is/was Jamie from Baccura who also modified Dahons into recumbents.