Well, it's been over four months since my last post! But don't worry, things are actually happening.
I'm about 80% of the way through porting Undiscovered Worlds. Regional maps are starting to look recognisable. I've done terrain, rivers, and lakes, which are the worst bits. Basically this process oscillates between, on the one hand, bafflement that things aren't working as they should and a resolve to give it all up and go back to the original version, and on the other, fixing the problems and feeling gleeful at how successful it all is. I'm hoping that I will end up in the latter state rather than the former.
Anyway, there isn't really anything to post about because I'm basically just re-implementing the stuff I've already described. There are some little tweaks along the way - among other things I think the lakes look rather better now than they did originally, which is nice - so I'm hoping it will all end up fairly decent. With luck it won't be too long now before I can release what I've got and then think about the next steps in worldbuilding.