Sorry about the derailment...back to the topic at hand...I'm running an Aeroflow large shield which is a GREAT all around shield and is good for warm weather due to the huge amount of air that flows to the torso with the shield at any height. Unfortunately all that air flow is cold in the winter. I have a couple of the larger stock shields, and I want to do something along the same lines as the OP to relieve the back pressure, while blocking the cold. I may try four 1-1.5" holes. two in the middle of the shield, and one on each outside edge.