2.5" baffles and you will have as much bottom end as a Vespa. I just tried a set of Twin Slash Ovals, (lasted one week), and the bottom suffered big time and they have 2.25" baffles. I might ad that the bike has true dual headers but still, I wouldn't even think of 2.5" baffles but I kind of like a little performance once in a while.

 

I took the baffles in my Rineharts out and widened the holes all the way around. It helped the sound tremendously.

 

4" mufflers sound a lot better than 3.5" mufflers - what do you have?