Im using a custom 4-4 exhaust and wanted baffles. Because they are megaphones, straight baffles wouldn't do it.
What to do for caps? CB500 ends cut from an old exhaust I had around. Fit perfectly on megaphone ends.
Then I got some exhaust adapters and ground out the caps till they fit in. 1 3/4" X 2 1/4"
Then I had my buddy flare the ends of the same types of adapters till they were a smooth flare from 2 3/4" to 1 3/4"
I used 1/8" perforated steel on 3/8" centers and rolled it around some exaust pipe till it fit into the 1/4" ends on both caps and flare, then welded it all solid
Then I rolled some steel till it fit in the megaphone ends and stuck out 1/2" for the cap to fit over
Then I did it 3 more times. Ill use small SS screws to hold the caps onto the megaphones. I will wrap them in SS silencing material after hot coating.