LSA or Duration to fine tune glasspacks??

If,... I was to run a GP, it would be as a resonator, well after the 3-pass, and it would be under the trunk about a foot or so from the end of the pipe, and followed by probably a turn-down,turned out a bit.By the time the exhaust gets this far along,it has cooled off a lot, and lost most of it's energy. So now it is ready to have the hi-frequency annoying sound energy, sucked into the matting