l had some rot in well all four 'exits' of my collector box. This is a 78 Kawasaki KZ1000 exhaust balancer pipe I used for the repair of the rear cyl females. I brazed it because it's all I have, there are no doubt better fits, but you get the idea, this one has about 1/2" less purchase on the down pipes but seems to work just fine. There is no gasket as before, but a copper collar/ packer made from a copper plumbing fitting about 1mm thick from the hardware store, with a good smear of red silicone for good measure
Sounds like your home fab solution has the matter sorted. Has the pipe been put back on and been tested? Is that high temp silicone you put on there? I was thinking that would cook off and disintegrate.
........................red silicone is a well known bathroom silicone, i thought it would stop the water getting in and rusting out the box
