the F7's among other A/M pipes, do not cone with a forestry approved spark arresters, as they are made for a track
i have heard of guys using 1/4" square hole chicken fence, and shoving a small, cup shaped piece into the silencer, that size holes will not obstruct anything, and if a forestry ranger decides to poke a stick in there to see if it's spark arrested, he'll hit the chicken wire and think it is
as thats the only test i have ever heard of them using, poke a wire/stick in there.
but with that pipe you may also be over the decibel levels some places enforce