DUDE! Nice work. I had this a repair too. I think every 17’er will. I wondered how bad it really looked inside and you have boldly gone where no man has gone before - with your camera.
I like the drainpipe and foam enclosure too-smart.
I had a really bad spiral fracture almost from top to bottom in the socket. I installed 3 stainless hose-clamps around the socket housing by opening them up completely and putting them back together around the socket. I placed one near the bottom, one up about 1/3 way and about another 1/3 above that. When I cranked them down, they pulled the fracture together. Like you, I left a piece of pipe in the socket (great minds eh?). So that the pipe would not get glued in place by any epoxy seeping through the repair, I put Vaseline on it. Also use vaseline to keep errant drops of epoxy from sticking to hands, decks, etc.
I put 3 layers of glass over EVERYTHING- including the clamps. I figure that leaving them in place could only add strength to the socket walls. I went to the starboard hull, which was not damaged, and installed clamps and glass hopefully to prevent damage in the future.
As you know, the fact that you are doing two-handed work with one hand through a 5 inch hole adds a certain sense of “adventure” to this repair. Judging by your photos, you had a good “helper” though.
If anyone is interested, look elsewhere on the H16 thread where I share my experience in adding deck hatches to a Hobie (or any boat- I also put hatches for access on my Catalina 25 and a porthole for light and air in the quarter berth) I guess I just like cutting holes in boats….
One other thing- a small hand held bilge pump fits nicely into the sockets for water removal. My wife would have a fit if she knew I used the turkey baster