Before cutting further holes in the side of the fuselage, I'd experiment with installing a 'T' in the scatt tube, running to a second eyeball vent. I've found the NACA scoops provide lots of air volume, usually ending up partially closing the eyeball vent to keep things flying around in the cockpit. The other thing of advantage (to me at least) would be to spread out the air flow over more of my body instead of the concentrated blast in my face or chest.