about 35%, the hardest part about painting it is getting it smooth...use the wrong paint and it will feel sandy to the touch.
if you can find a 'shiny' type of primer, they work the best.
how about sand blasting it? then polishing... the top of the fins would be shiny and inside the fins would be a flat finish...two tone, thatll be pretty cool.
one time i took an amp to a machine shop and had them mill the fins like a wave.