A ¼-20 stainless-steel button head screw is used to secure the other side (bottom) of the reducer to the muffler.  If an O2 sensor bung is not installed, substitute a ¼-20 stainless-steel button head screw on the top to lock the reducer to the muffler.  The joint between the reducer and muffler is sealed with JB Weld Extreme Heat paste.  Once it’s all together, it’s not advisable to try and take it apart.  You must make sure everything is right before you assemble it.  Several dry fit-ups are in order before final assembly.  Before you assemble the reducer to the muffler, make sure the adapter bushing is installed in the reducer.

This shows the ¼-20 screw installed in the bottom of the joint.

Lock the baffle assembly in the muffler with suitable stainless-steel screws.  The screws are threaded into the adapter bushing.  Stainless-steel countersunk screws (8-32) fit just right.  Put a dab of Permatex Optimum Black or Grey sealant on the threads prior to installing the screws.  It keeps the screws from coming loose.  The Permatex Optimum grade sealants can take the heat.

Maybe later I will see if I can come up with a mount that can be attached to the muffler with stainless-steel pop-rivets.

Awesome!
Thanks for sharing your hard work!

Fantastic write-up,  Mike- I suppose all your tube diameters complement your large bore cylinder?   I've got a stock header and a carb jetted to a Harley muffler- all that talk about no flow being too much- were you speaking to your circumstance,  or mine?   "Unlearning" a truism, I seem to be resisting adjustment.

Mavigogun, I did all the tests on my 94mm engine.  Once I finished up with the muffler project, I pulled the 94mm engine and installed the 97mm.  The 97mm runs great with this muffler too, but the improvement is not nearly as dramatic as it was on the 94mm.  I'm not sure why.  The two engines have different cams and exhaust ports.  The 94mm has a hotter cam and a smaller exhaust port, while the cam in the 97mm is a lot milder but the exhaust port is larger.  It could be that the bigger bore engine wants a muffler that flows more, or the smaller engine has a cam that works better with this muffler.  However, the muffler works superb on either engine.

Regarding the flow, I'm a firm believer in achieving the highest flow possible without setting up a reversion problem.  No sense installing a bunch of high performance components and then choking off the exhaust.  Big carburetors, cams, porting, air filters are all intended to move more air through the engine.  How can choking off the exhaust system help?  My best acceleration times were using a wide open cherry bomb glass pack.  It was only .04" (1mm) smaller in diameter than the header.  Street manners were just fine, not a hint of reversion.  Must not take much to break up the resonant wave. 

Hiko, many mufflers are made exactly like this one.  A good example is the Dyna muffler.  It uses a similar baffle design and absorbent material in the outer shell.  But the baffle diameter is a lot smaller and there are fewer perforations in the baffle.  These reductions are necessary to allow the muffler to meet federal standards.  Both the stock LS650 muffler and the Dyna muffler have notes stamped into their shell stating that the muffler meets a federal standard of 80 dB.  This HighFlo muffler is quiet but I don't think it meets that standard.  It is certainly quieter than any other aftermarket muffler I have heard.  

Good luck with the wide open muffler MMRanch.  I suspect it's gonna be a bit on the loud side.  I put an additional baffle in a 1.75" cherry bomb and it took the bite right out of it.  Unfortunately, the additional baffle also brought the flow down to the same level as a Dyna muffler.  It ran good and sounded good, but just didn't have the flow I was looking for.  It's the size of the baffle.  You can only fit about a 1" baffle tube in that 1.75" muffler.