I had fairly good results with using just silicon. I am putting o-rings on my manifolds to try and get it 100% sealed.
My carbon cans started to slog out at the rivets, again. I have replaced the rivets with shiny mushroom socket head screws.
The inner perforated tube in my cans was also rattling about, wearing on the aluminum ends and causing a grey spooge to leak out of the exhaust end of the loose rivet joint. I used epoxy to glue the perforated tube into the end of the aluminum end cap to stop it rattling around. Hopefully another small problem solved.