rmh

much of the calculated info is NWAS.
why?
because it does not include full throttlability required
Plus NONE of the BS (Facts about tuned pipes)I have read ever included pressure readings and without that - it is a crapshoot .
Your gues if it works and is smoothe with no flatspots - beats all the calulated crap.
How to do it right ?
really takes experimentation as the rpm is a prime factor
Do this first
establish a rpm baseline with NO exhaust system - wide open tuned for full power (don't overheat it
Decide if you want a severe noise reduction with no power losses or good noise reduction with a little power increase.
look at the pictures attached -these designs work but they must be sized close to correctly and there needs be about 1/2psi in main chamber at full power
a paint can can be used a steel paint can is a good one to use - and tubing for stinger - just KSbrass hobby shop tubing
The larger the better -within reason
small touch up cans for under 26cc and slim to std paint cans on 50 60cc.
You must try carefullysqueezing off the stinger to see how it affects overall performance. this changes pressure
The muffled only setup can run a very short header but can should be quite large - NOTE it is the drawing with the tube stopping way short of a baffle
these are blatent copies of existing commercial mufflers -cans - I have no pride