You could think of another concept. Having one unit with full opacity, and the other one diagionally have less opacity isn't how i would do it.
I suggest simply showing a pic of arm, and then like having a duplicate with lower opacity, with tweaking, making it look like it comes from the original, a sort of propulsion effect.
Well, your mirror image, honestly, looks like awesome and is a very creative idea to do this, i wouldnt have tho about it myself.
and dude, wtf, are you 5 years old? make him a neck, it looks like really bad without it. it's not much of work, do his throat, and a bit of upper body. if you don't do it, that will be a shame, a lame shame, really.
Don't do like the XMAN fanatic guy, complete your skin each by one with care, not quickly doing a skin with urge and then jumping to the other without having took efforts to do the first one.