Welcome to the HUBB Ian,
There has been endless discussion on here about every aspect of bike selection, from just about every angle, so it might pay to have another trawl through the previous posts in this section.
Personally I'd consider the DR650 if you're going to be primarily one up.
It'll take the weight fine, especially if you're not going too off-road. I just spent 6 weeks biking in cambodia, looking for the most interesting 'roads', and I know what you mean about the terrain.
Other bikes that are often considered for this kind of trip are the yamaha XT's, BMW F650, Honda Africa Twin/transalp, and bigger beamers.
Some other important considerations may be where you're going to buy the bike and cost of the carnet.
Best of luck, and enjoy the trip!