The gutter being glued in. I had to make some special blocks to clamp it in place. Just barely had enough spring clamps to do the job. I will most likely have to get more so I can glue both sides in at once. The adhesive I use takes a few hours to set. Here's what it looks like once the clamps are removed and the drain tube installed.
Closeup of the drain tube. A bit of silicone seals it to the gutter and holds it in place on the side of the shell. I shape the top of the tube with heat to fit the inside of the gutter and prevent it from pulling out of the gutter.