id take back the return edge on the armor..should only be about 1/8th inch. Its making the armor look too thick.
Hmmm the collar does appear to be small. My honest opinion, you should probably replace the chest/ab/collar and back with pieces from
animefan or
Wasted Fett. Although RKDs armor is probably the best quality out there, i always felt the shapes were a touch off on the chest pieces and the return edges slope slightly outward rather than straight back which i feel gives it an odd look. I think Animefan or WF's armor would fit you better in the chest/chest collar. I know thats not the answer you wanna hear, but i think it would get you to the best look possible.