in fitting an ANH butt join, you cut off both halves of the overlap so that they meet in the middle.
when fitting just cut off enough overlap so that it fits your body, but not too tight. you need to be able to move!
when the overlaps are cut evenly and balanced then with the finishing strip top it off!
it can also be a little easier if you put a small strip inside to help keep it lined up.
from the photo shown of your forearm part the top seems to have had a lot trimmed off
and the lower portion still has quite a bit left on. the top part from your photo shows that you might
have completely trimmed off the upper overlap, and now you're into the armor itself and
trying to line it up?
to get a balanced look you simply have to take the same amounts of overlap on each side
this might explain why you're arms are not lining up the way you want.
and the AM kit is not screen lineage so making shape adjustments to the overall
to resemble screen used, such as boiling water and the like might make things more difficult
than they need to be.