Cutting the front of the cowl will cause it to overheat. High pressure in the cowl will stop airflow. You want low pressure in the cowl so air will flow through the inlets. But since you have already done it, and you say you have a 2 1/2 to 1 ratio, you should be OK.

I've actually closed down inlet area to increase airflow before. The Bonanza pic shows how it was done to establish the correct ratio.