Okay, I've created a map of tectonic plates, which should help me visualize where mountains should go:
TectonicPlates.png
So, from what I understand, mountains should go along B and C. I'm not sure if they should go along the coasts of A and B, though. And while I'm examining my image, I think I should change the direction of F to go north to get mountains along F and B. I think that's about it for the boundaries... Is there anything I've missed?