Gordon Jennings notes stinger ID is about 60% of the header ID. And the stinger length is 12x that number.
The narrower and longer a stinger, the more pressure and hotter the piston crown temp.
Looking at circuit pipes - they are designed for low end by way of pressure build up. What is the safe limit of these pipes on a bike running "safe" timing? Looking at some 2t pipes, these "rules" arent followed.