I hadn't noticed the tropical aspect: interesting how different people get different impressions! If anything I thought Sentinel Island was more hot and desert-like, whereas Fort Joy felt to me more like a sort rainy part of northern England. Which is probably not very imaginative of me since that's where I'm from.
You may be right about the harbour, but on the other hand it seems it is the only useful harbour on the whole island: the only other harbour is also on the north side next to the fort itself, and judging by the number of wrecks it doesn't seem especially safe... so I'd hazard a guess it's not necessarily indicative of the direction of sea traffic, but it may be.
One thing that does occur to me is that in Ego Draconis, there's no port or coastal town shown in the Fjords but there probably would be one somewhere, I would guess more likely to the south as the north looks to me to be increasingly impassable: given that it is a major inland route to various other settlements my river, road and zeppelin there must be one somewhere, and the Champions' fort doesn't count as that seems to be dedicated to a military stopping off point. Whether or not Arx might be that coastal town or city is anyone's guess, but there must be some fairly major coastal town(s) in that area.
