Okay, I've created a map of tectonic plates, which should help me visualize where mountains should go:
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?
Looks good. Maybe someone with more experience in tectonics can help you refine it or answer questions. I am not enough-so to be offering any thoughts or advice. But I wish you luck.
TombRaiderJake, sorry for the tone of this reply, but I have looked at your map for a while trying to find things to say and I just couldn't find anything plausible in it.
It very much seems you got your landmass shape from a cloud noise and then added random lines on top of it and called it plate tectonics. Inner seas and peninsulas normally are indications of plate limits, in your case I can't work them out.
Here's what I recommend: either do an entire planet and use this shape (or parts of it) there, or decide on a smaller scale and just ignore tectonics.