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I am sure the effect is tiny but every little helps.
This is a case where there is so much noise, little bits don't help much. Humans have such good senses, reducing the sound level by half is only just barely discernable to a person. They measure these things on exponential scales.
The biggest effect comes from having some resistance after the muffler. So moving the muffler towards the V band will help a great deal, every single inch. Having a 90 degree bend after the muffler also helps a great deal. The idea is you need some resistance after the muffler to force the exhaust gasses to dissipate and spread out over time in the muffler. This should not really affect your power.
Sport motorcycles achieve amazing power levels in stock form and yet make little noise. They tend to have small muffler exits. Many street cars have fake exhaust exits that look big, but if you are stopped behind a Porsche or BMW or other high powered car and can look up the tailpipe you will see the exit from the muffler is rather small.
Maybe you can get a little collection of 90 degree bends with a reducer after them or welded up with a piece of a reducer and experiment until you get what you want. You can probably buy those parts for playing with for $10... Then make sometthing nice.