Hello Jim. No pics and I apologize for not doing so. I can try this weekend. As far as a second hole, what I'm referring to is drilling a second hole through the interior bulkhead adjacent to the Factory's readily unseen single outlet through the rear bulkhead.
If you look up the outlet of the stock muffler you'll first see a curved 1 3/4" tube welded to the very outlet. It curves to the right and looks forward at a bulkhead. That stainless steel bulkhead separates the cat convertor from the rear muffler chamber. The bulkhead has a "X" formed in it (for structural strength I assume.) You can see the bulkhead and X through the tube with a flashlight.
With a 1 1/2" hole saw snaked in through that curved tube on a 24" drill extension (2x12" coupled) I drilled a hole through the X. I then enlarged it to 1 3/4" with an abrasive flapper wheel as described earlier.
As mentioned the first hole through that baffle is unseen, but it's a straight 1 3/4" tube welded to the bulkhead and parallels the curved tube on the left muffler side stopping just short of the outlet. Put a small mirror up the curved tube and you'll see it. It carries the exhaust gas to the rear of the muffler from the cat chamber. The flowing exhaust gas then makes a 180 deg turn forward to the curved tube's inlet, followed by a 180 deg turn out the curved tube to the rear of the assembly. Adding a second hole simply straightens and increases the flow to the outlet tube, which remains at 1 3/4" due to the muffler's design. It's louder, lower in sound, but not obnoxious. And the mod retains the cat for emission purposes.
Gary in Alaska