Sorry, I'm horrible at pics and videos. I get mentally absorbed in the process and completely forget.
I started off cutting a 4x4in square out of the bottom, but wasn't able to get everything out that way. Took a couple pics then but no videos and they ended up being irrelevant. welded the square piece back on, installed it and decided it wasn't enough. Slightly louder and no better.
At that point I put the stock back on and just decided to cut the modified one in half as a last ditch effort. Didn't really expect better results, but I had nothing to lose. should have done this from the start.
Just cut in half on a band saw from the front to the back at a point where you're not disturbing the brackets. You cut right through the cat. Once it's two pieces, you have to do a couple passes with a cuttoff wheel on a grinder to get to the base of the cat on each side. There's a lot of bracing at the inlet side of the cat that can be removed to open up the path between the inlet and right side outlet tubes. I probably spent more time removing cat bracing than I needed to, but again, at this point this was more for grins and giggles than any expected result. Welding back together was easy. I was worried that if I didn't get the welding of the two halves perfect I wouldn't be able to get it back on the bike, but even with a little displacement, it went back on fine.
Not sure what part of this improved the sound so much over the 4in cutout method, but it did. Would it be easier or harder than Meerkat? No idea. Better sound? No idea. Just something about the Meerkat method (Horrible flow transitions and heavy piece of cat material left in place) that just bothers my engineer brain. So take all of this with a huge grain of salt, but I do think anyone with a band saw, welder and a bag of cutoff wheels can do this.
Definitely use good PPE (respirator and goggles) when going at the cat material. Of course the resulting bike is for closed course use only