Tip of the day:
My CP23 came this way from a prior owner, and I've been doing it like this since on several boats.
When you install your anchor line, tie the bitter end to a 6-8" hardwood dowel or stick that won't pull through the hawse pipe sideways.
You can insert it down through the hole, and when deploying your anchor you won't lose the end of the line.
But if you want to get to the end (to remove the line so you can wash it, or to tie on additional scope) you can rotate the stick and get the line out without having to go down below and untie it from something.
Mark your line with red tape or something so you know when you are getting close to the end.
For my CP27 I used a piece of old closet clothes hanging rod sawed off, it was large enough in diameter I could drill a hole through it instead of tying it around. Even less chance of the rope slipping off the end of the stick.
(http://i1299.photobucket.com/albums/ag73/relamb01/IMG_20170508_152643676_zpsj8ytr5sw.jpg)
(http://i1299.photobucket.com/albums/ag73/relamb01/IMG_20170508_160324488_zps1fbf938q.jpg)
I did something similar but not nearly as nice. Good job and a great post!
I saw a boat where someone with an oval hawse pipe had cut a circle of 1/2" plywood with a hole saw, with a hole in the middle and the stopper knot. That would work as well.