We install drop tubes last. We custom-made them by shaping an 8-inch-wide piece of copper over a piece of pipe and closed the tube with a single-lock seam.
…then pounded down the top 3/8 inch with a hammer, creating a flange that would seat itself against the trough bottom. Copper is only so malleable—any more than a 3/8-inch flange and it will tear.
A typical flaw with older built-in gutters is undersized drop tubes—I’ve seen them with diameters as small as 1 inch. For this gutter, the 3-inch-diameter drops should suffice.
…we were ready to drill a 3-inch-diameter hole through the copper liner, plywood trough, and pine soffit on site.