Very nice style! I like your color choices and the look of your lines.

Based on the disposition of the mountains on your main landmass, I'd expect your big island to be around 150 miles at its widest point--from the marked city to the end of the cape west-southwest.

That would make the large landmass a bit larger than the peninsula containing Burma, Thailand, Laos, Vietnam, Cambodia, and Malaysia.

That may be a bit small for you, though, with your big island having probably just a little bit more land area than the island of Hokkaido in Japan.