hit and miss ventilation grilles in Cold frame

I have harvested 3 opening double gazed windows and I'm building a cold frame with them 1.425mm wide x 760mm deep x 300mm in the front and 400mm at the rear. As this cold frame is going to the allotment and I'm not going to be able to visit every day - I was thinking of drilling holes in the sides and covering with some old hit and miss ventilation grilles that I've just replaced - Any thoughts or suggestions?