Hi MrBrown, ZoneRanger & CrimsonEclipse,
Thanks for all your information. After speaking with J at Gaerlan Custom Cycles in California (who seems very knowledgeable about Dahons in particular and touring on folders in general), I've decided to purchase the Mu P24 and get a spare rear wheel without the dual drive. I was thinking of getting the P8 instead, because the wheel has quick release and is easier to take on and off than the dual drive train wheel on the P24, but after considering the price differential, and the fact that I might want the 24 gears in the future, I decided to do it this way. J advised that the dual drive wheel is fragile for air travel, and difficult to take the wheel on and off, so I'm going to leave the dual drive wheel at home for my first overseas trip with the Dahon. He's going to change out the front ring for me to allow lower gearing for climbing hills. I plan to get front and rear racks, with a trunk bag and possibly panniers on the front (J thinks that they shouldn't be a problem, especially if not loaded too heavily. Standing on the bike while climbing is the real problem for the headset).
I'll let you know how it all goes! Thanks again.
Basia