[chris.817]

The one-in I saw was one long perforated tube that went the length of the can, left to right of course, and back to a left outlet.

You'd have to do a lot of hacking of the can to figure out where/how to put the ins and outs. Then weld inside to the perforated tube. Close the can back up and weld that. I've not seen this done just how I imagine it would work knowing what little I know.

My muffler ids a stock 1in, 1out with a second out added straight from the baffled area. The difference is that both outs are on the same side and looks like a turbo outlet. Sounds great too. Many folks that add a second out like this do it to the other side and complain about resonation.

I don't think it's nearly as simple as it seems it would be...