does anyone know if the icon will preform well in a 3 cu ft. ported box? 3 cubes is all i can fit in my CRX since i want to keep the sub covered.

any input would be great

The 15" Icon would be fine in a 3.0. Tune it in the 30hz range, give it a little bit of polyfill and let it fly.

if im going to do a 6" aero, how much polyfill do i put it? Also wouldn't the polyfill fly out the port?

The amount of fill depends on testing and how you like it. Keep in mind once broken in the sound and output will improve. Also, if you put a dab of glue on the polyfill, it won't fly anywhere.