MS, good job.
They say great minds think alike. Do you think they sometimes think in reverse? Last night and today, I was mulling over sawing the backside off the muffler versus cutting off both front and back. Either way would require a fan shroud. I was bemoaning the fact that I can't weld or braze - shoot I can't even solder - so I just check in here and what do I find -your handy work!
I am also mentally exploring a different route altogether. Have you followed the flow in the 800 muffler? Some of the exhaust is directed to the side given the shape of the exhaust port. It is then bounced around in the can only to flow 90* straight up just to hit a flat surface to be directed 90* back where it hits a divider to disperse it around the screen. My thoughts were to outlet out the front or front clutch side. I fell back to the front as a first try - but alas without nuts and bolts I can't put two pieces of metal together.
Ron