Yea I cut from both of them. when you overlap them, you could see what you need to cut. unfortunately for us there's no cover strip area like the other armors have, so I suggest cut half of what you plan on trimming and do a little at a time.
Ill try messing with pieces I have cut already and see what it looks like bending with heat. just a little scared being my first armor, tend to be over careful with pricey toys lol.
Answer: Im not sure, with this side I think I'm going to go your rout the long way, however I've seen pictures of it being done from the inner part of both sides then the outside. If you try to do all at once, you might have pieces shift off place because of too much glue in its gel state.