If there is no venting at the bottom of the valleys the plastic will chill off long before enough vacuum will be pulled in this area. With 40 mil matrerial you could get by with .032 drill bits. but with it being a lense construct you would probably want to vent with a drill in the 70 to 80 regions. Another thing to consider is that pet likes hot molds. If you want super detail you are going to have to pressure form.