Tips to quiet down exhaust?

[Stubbz63]

ill have to take a fresh pic for that dont think i have any directly from the back of it. i took my spark arrester i had left over from my fmf powercore and started the bike and just held it in there its a little small in diameter and deff quieted it down some but im not sure how i can get it mounted in there without it rattling like crazy. id like it even a bit quieter than what it was with even that in it but that helped, just gotta figure out a way to mount it.

ill see if i got any pix showing the back end.