Yep Marvin is the EVA man.
I will add my tip for drilling it though. Get a oc of metal tubing for what ever size you want the bore to be.(smaller then your mouthpiece)
Take a counter sink or what ever cuts a taper and bring the edge razor sharp. Now you have a hallow cutter that you can core out the hole. Makes a super clean cut much better then anything I have tried.
If you like spending money. Go to update. Its a lithographers supply company. Look up paper drill bits and pick your size of the cheapest bit. Your only cutting foam.