@Gandwarf: Thanks. I'm not 100% sure that my hydrology will stand up to the river police and I need to look at it again. Many of the largest of those are supposed to be very deep, according to my backstory, and surrounded by higher ground. Not sure that gets around the need to have them drain on the surface to the sea. Imma consult some real maps again before I finalize those. I have another problem with rivers in that I had intended at least one to get to the northeast coast, where my city Haibianr is supposed to sit - but I ended up making a pretty solid wall of mountains over there.
M