[olddog]

My side pipes were originally a slip fit that leaked. I had 3/8" plates made and welded them on myself. I have 3 bolt on all 4 edges that makes 8 bolts total. They are 5/16" - 18 bolt. I used stainless steel bolts and nuts, which tend to seize easily. Steel bolts may not need anti-seize, I wouldn't try stainless steel without it.

I made aluminum gaskets. I think the aluminum was about 0.100" thick. I used flat washers and torqued the bolt to their torque spec. I ran it through a few heat cycles and re-torqued the bolts. Never had any problem with them coming loose.

I would think the copper gasket would be better than aluminum. Sounds like others are having problems. I cannot say why I am not having the problem. Maybe something here in my setup is different and you can spot it. Good luck.