I run a similar setup with fishtails. I'd recommend a 4" "beer can" type baffle. They won't take too much sound away and will give you positive back pressure.

Something like this:


2002 Bandit 1200/ GSXR cams/ 1277 BB Kit/ Holeshot header and can/ 38mm flatslides/ a good head/lotsa hp/lotsa tq- lots of rear tires...