I made up a new set of baffles, using the basic design from Car Chemistry in heavier material and larger mounting rings to yield more sound deading volume. They're basically a piece of 2.25" exhaust pipe (originals were 1.75"), a couple of pieces of 0.125" plate with 2.25" holes cut to make big "washers", and a pair of donuts of larger exhaust pipe, one 3" and one 4". Each donut is welded to a "washer", then positioned on the baffle pipe such that they wedge snugly into the megaphone.

They slide into the laker megaphone, fitting nearly flush with the end:
Baffles 024.JPG

The outboard ring has about 1/2" of room between the baffle pipe and the ID of the 4" ring:
Baffles 025.JPG

And they whole baffle:
Baffles 026.JPG

On my store bought set the baffle rings were stamped steel, something like 14 gauge, and I had one mounting screw through the bottom side of the header, screwing into a nut welded onto the baffle ID. Over time the heat and pressure of the exhaust warped the baffle plate quite a bit, and they rattled a bit at certain points in the exhaust flow, like decreasing rpm's under load.

Anyone have a better idea for mounting? I've considered the expanding capture nuts at 180* on the header, attached to the baffle ring to accept 1/4x20 button heads, but I'd have to tweak the baffle plate for clearance as they need to fit very snug and drilling to hit the center to the baffle plate is dicey. I've also considered some sort of "ring" that slides back against the outside of the baffle ring with three legs welded , each thick enough to be threaded 1/4x20. This would yield three holes spaced 120*, near the end of the header. I'm open to suggestions or ideas, as I'm still deep in the thinking mode on mounting.