Ya you definately don't want it blowing right on the brake cable, not to mention the back wheel. On mine, I used a 8" or 9" extension pipe at back of header pipe, with the bend in it, and then the torpedo HD muffler. Mine ends up blowing out past the brake works.
As far as the washer thing, mine was tapped into the front of the muffler, up against the old baffle. Someone before me had knocked the center of baffle out. The washer just made the hole smaller, but there is still air flow around and through the baffle, as was originally intended. So, I'm not choking it off any, just redirecting it some. Not too loud, not too quiet.
As you can see in the pic, I still have a leak where extension pipe and muffler come together. I was thinking of getting it welded. I would do that before using tin cans and u-bolts.