The engineering triumvirate for mufflers will always involve various combinations and compromises of the elements a) size (weight and volume) b) efficiency (flow) and c) noise. A tiny muffler that is both quiet and flows well is the target everyone (well, almost everyone) would shoot for, but nobody could ever hit. (Look at Harley Davidson's agonizing job to design a suitable muffler for their purposes on the V-Rod) So, compromise is the name of the game, how big, how quiet, how much performance is expected. If your muffler is smaller than a stock one, and about as loud, chances are it will be somewhat restrictive - but there's nothing wrong with that; everybody who attempts this faces the same problems, and will be making concessions in some area.
That said, it looks completely workable to me - good job. I have seen motors that go so far as to be difficult to even start with some exhaust/muffler configurations (the proverbial potato in the exhaust pipe), and your bike wasn't harder to start, so good on you - you have already ventured where few would dare, and though the depth of this field is almost infinite, since the decisions are personal choices, you are best-equipped to judge the relative success of your efforts.
