[Jack21]

Have a CR, not BDR, but here are a couple of suggestions gleaned wrestling with CR exhaust issues.

Eliminate engine movement that causes exhaust flexing by using polyurethane motor and trans mounts made by Energy Suspension. They soak up vibration and noise, but hold the engine solid so it doesn't move around. Car rocks a little with engine idling. It's this rocking and flexing of the exhaust when using standard rubber engine mounts that's making the exhaust leak. Worse, if the joint isn't allowed to flex, it will eventually break.

Support turn out exhaust exit with rubber grommet, or strap that allows side pipe some movement.

Now, your Ultra Copper may seal your joint. This stuff seals exhaust gaskets quite well. That's what it's made for.

Failing that, weld a flange connector on both ends, between J pipe and muffler, and bolt it together. Use copper gasket, and RTV to seal.