I would skip shrouding the feed and just replace it. You already have to drilla great big long bugger of a hole, you might as well just drill it the right size and make it the tube.
You might as well just go trigun, just put in two feeds, they will line up you know.
I think I figured out how to get rid of the cylinder pin altogether. I had a mad thought the other night. Needs experimention along with the other 37 things i have to test out, and the parts I need to complete. Its a never ending story.