I use a muffler(s), with 600mmm of perforated core alone, on my bike.
So I can ride virtually anywhere, and people don't hear me.
I've got probably 8 mufflers hanging up in my workshop, for my bike, and just use the 2 looooong ones I made - one is a big size , fairly thick walled , oval canister, to take the abuse in amongst all our rocks, the other, a small outer dia., thin walled one. Both are as quiet as can be.
The thing is, the bike is a 500, and I don't notice Any power loss at all............ it actually smooths out the bottom end / mid range hit. But when I put on my short PC 11, I don't notice much extra power at all, just a hell of a lot of extra noise, that would bring the local authorities down hard on me, as they do with all the drongos with their Loud 4ts. The first thing the 4t riders seem to do, is throw on the loudest pipe they can find, and then they wonder why the locals bitch to the Police, and they get harassed. The local cops know me and my bike, and I get waved on by them, going into , through, and out the trails, quite often, as they are booking gooses on their loud (inevitably) 4t bikes.