Many holes drilled around the perimeter is probably best then. Then a simple hole saw would probably open it up.
Jigsaws are pretty useful and cheap. If you're in west county pm me and I might be able to get you a tool.
Neil -- "Easy Bake Master"
NB Bandera [gone to heaven...conveniently located in Long Island, NY]
Rebel 23, WSM A, WSM B, UDS, Easy Bake Oven
Pork Pistols BBQ
MOINK...It's what's for linner.