Just a thought: Even if it WERE possible to crop this game via MAME, after you fit it to the bezel the aspect ratio would be so stretched that it would be annoying. I'm opting to do the same thing with this that I did with Battle Zone: have one metrically-accurate cabinet view for reference that's not playable, and this one that's slightly altered to make the game playable.
[ATTACHED IMAGE - CLICK FOR FULL SIZE]
I asked my cat what the meaning of life was... he noserized me and stuck his butt in my face.
My MAME/MESS artwork files: https://drive.google.com/open?id=1ABxeKgNIrKlIsyck7dx4V241NFQDWAF4
Related screen shots: https://drive.google.com/open?id=1U5IbvbVzYW97PuOOQuocvZFE_YJz7WIn