I seem to remember it's a 1" hole I drilled with a 1/4" 12" long bit to insure placement, then used a hole saw. Used a burr to create a small radius on both sides to fit the tube. Almost positive Tim and I borrowed your tool to install the brass piece. I used a liberal amount of the 3M adhesive/RTV 5200 to seal it up, but I didn't perform any other resin/acetone there. It's been since painted on the inside, so I hope it's good.