I did this myself. It's a G1 arm cannon, which is much better for size. I cut into the MP arm mount on both sides so the locking part of the cannon clips onto it correctly. It looks very good, and is clean. Comes with no other parts - just the figure. Figure is C9 or better awesome. Has minor dust, if anything.

I would sell or probably trade this, but I prefer to ship upon receipt. I have loads of Ebay feedback. Looking for other MP's, PVC, micro six teams, reissues, etc.