I currently have 1" drain lines on my rear bags but still have the 3/4 in thru-hulls. I have two questions that I'm pondering: 1) how to enlarge the hole to accept the 1" thru-hull. Since there's already a hole there, the pilot bit for a hole saw has nothing to guide it. 2) It is currently 3/4" for only 6 inches right at the fitting itself. Is this really restricting flow significantly?