FMF Turbine Core II silencers is the way I would go. They are about the best performing spark arrestor. Way better than the clamp on sparkies. Just sell your Power Core II's and buy the Turbine Core II's and dont look back.
I dont know why FMF doesnt show an application for the banshee. They are 240 range on ebay.
Just make sure where ever you get them from they are for FMF Fatties. The fatty and gnarly use the same silencers, the FMF SST uses different silencers, they have a shorter stinger tube.
josh
Turbine Core II's Ebay LINK
Turbine Core II LINK