~steve.
Yes.
Stinger's job is to keep proper pressure in pipe. It's also good to be long enought, that shock wave not ended too soon. If back pressure is too low you lost little bit power. If back pressure is too high you get little more power, but your engine going hotter and hotter and start knocking. You must retard ignition or lower compression.
Is this importing in 500cc motocross bike? 125cc World Champion RR-bike is different thing. They have fully programmable ignition with data acquisition. Cylinder head exchangeable with combustion chamber. Then you can once in a blue moon play with back pressure, "put washer beginning of stinger". This is my 2 cent.
I have made only one exhaust pipe (to my old "RR-KX"), so i'm not some pipe guru. I hope that i could make some other pipes, but seem quite bad.
MuN
PS. Couple years ago my wife want water to backyard. I draw through two wall about 8m long and 8mm diam. copper pipe from garage to backyard. Water coming like my piss (old man)
. I changed pipeline from 8mm to 10mm and now water have pressure and coming fine. Note! The short output in garage is still 8mm! ("put washer beginning of stinger")