the reason Calmini charges so much for their cone filter, is that it comes with a metal bracket that uses the stock air box bolts. It make the cone filter stable so as not to flap around and get damaged. it connects to one of the MAFS(Mass Air Flow Sensor) bolts and I can't remember if one or two of the air box hole locations...but as always save all of your stock mounting hardware.

If you check my Gallery, you can see a pic of my Dual Optima setup with the cone filter. Removal of the airbox allows for very tight installation for another battery.