We have the tin up on the shed roof for the outdoor kitchen. It is an open air kitchen and so we are not trying to totally keep it dry. I know rain will blow in here and there. The roof is to keep it mostly dry and keep hard rain off the Cob Cook Oven and the other ovens. So - we have the tin roof on. Now, how to cut the hole in the tin so that the stove pipe for the wood ovens can go out the top? I know to buy the rubber boot thing or a metal boot thing for the top side. But how to cut the hole? Would we just poke a hole with a nail and then cut with tin cutters? Or do we cut it with a saw-saw? Should we make a mark around circle so we measure it first and then try to keep to that line? Tips and instruction please! Thank you.