3 stage under seat header pipes is what I use, Doug.
My GX-200 , I use that & a RLV 91 screw in mini muffler, which the threaded inlet ID is bored out ''a lot '' so it's not restricted.
I then cut off the 3rd. stage of the pipe to clamp the muffler inside the 2nd stage, using an RLV 1' clamp, plus the clamp to secure one end of the hanger strap/ bracket.
Cutting off the 3rd stage also sets the muffler from sticking out the back of the bike.
It is super quite, but still sounds great.
I
View attachment 258805