Saildan seems to know his Sunfish.
I joined the group you recommended - wow, what a resource library of guides and information - and help. :dance:
I forgot about that drain plug they put on the edge of the deck. The problem with that is you have to stand the boat up on it's side for the drain to work and a hull full of water can be quite heavy. At the junior sailing program I worked at last summer with Sunfish (& juniors of course) they had installed a drain plug on the transom that allowed a boat dragged up on the incline of the beach to drain.
I've read the side drain placement choice is so the boat is easy for a youngster to roll up and check daily. If there's no incline, lifting the bow is a whole bunch more difficult for kids.
I see in the view of the inside you could drill a drain outlet where floatation is and it wouldn't drain then. I think a sloshing boat is a one time issue - you get fixed, daily checking is an always thing and the easier the better for all circumstances, not just when you find a slope to drag the boat up.
- you could also put a few things in there: lunch, drinks etc.
If you get one with a bag liner - or else you might loose that stuff inside.
Many of the older Sunfish hulls seem to absorb water when in use, even if they started their lives out as 'water tight'.
I don't know about "absorb". I get the impression because this style boat is light weight for single handling even by kids they get beat. People are said to ground the daggerboard and crack the hull - stuff like that. There's a simple test they show that finds all the leaks. There's lots of guides to fixing the hull back to water tight.
There is an issue I see motor boats have with their flotation that these boats could have too if water inside gets ignored for a long time. Closed cell floats gets water in them when they get steamed in an enclosed hull sitting in the sun. That group shows the technical explaination and how to dry it back to like new. I had to do that for my boat and it worked.