If you use the Cobra toss the hose clamp crap, drill some holes, and use 3-4 sheet metal screws to attach the thing, with some star-washers. I used to run one on my 94 YZ125, I can't count the number of times I went back on the trail to try and find it.
And as KXtrailrider said, repack your silencer often and you should be alright on sound. And keep the screen clean! My bike ran on the rich side and I had the spark arrestor clog up on me more than once. I usually used a torch to burn all the crap out of the screen. If I knew how to jet back then I probably wouldn't have that problem at all.