I haven't done it for a couple of reasons- 1) I mostly use a slip-ring anchor that fits in the locker and I have other, higher-priority projects to spend time on. When I need to use my larger anchor, I stow it in the fish box up front. 2) I don't want to have the locker drain into the bilge. If I do ever get around to making this modification, I'll try to figure out a way to hook up the anchor locker drain hose to the PVC insert.
I've seen other people post that they use either a Chene anchor or a navy anchor that will fit in the locker. It sucks that the boat designers didn't provide more space in the locker, but at least you have some options.
