Thanks for the tip about GProjector, I'll give it a go!

Incidentally - re plate tectonics, we only have the exampe of Earth to go by, we really don't know how it would work on other planets. Mars may have had plates in the past (we can guess this from the Chasmas), but we don't understand how they worked. Personally I have an idea of tectonics for my own world(s), but I wouldn't get too bogged down by the technicalities.