I need to put a through deck fitting in my '76 Catalina 27. The holding tank was originally plumbed to drain out through a through hull, but as we all know that is now illegal. I have all the fittings, removed the old stuff, and now I need to drill through the deck. the question is - is there a diagram or plan or something to show where I should drill? it looks like an inch or so back from the stanchion.