My winter project is finally mounted on the boat! You may not be able to see it easily in the photos, but the bottom wooden step has a two step stainless steel folding ladder bolted to it. Here's the pros and cons of this design:
Pros
Bottom step sits right at water level while stainless ladder extends about 2 feet under for easy boarding
Removable with two pins at top (mounted with two anchor chain stoppers at top, and removable hinges at bottom)
Release cord extends to inches of the water level
Folds up within the dimentions of the transom
The edge of the wood sides that touch the transom has a cured strip of silicone to provide cushioning and prevent sliding
Wide wood steps are much more comfortable than small stainless steps
Cons
The center-mounted solar panel needs to be moved, it's impossible to climb into the boat with it where it currently is
Clam-shell exhaust vent causes exhaust back-flow into the cockpit and needs to be removed
Folding/retracting the ladder requires leaning over the back of the boat under the railing. Need to install a rope to pull it up.
It blocks the original white navigation light
Even after moving the solar panel, I'll either have to climb over the railing, or modify the railing with a gate
When installing the port side lower hinge, I stripped the heads off of all three screws
One more thing to varnish
No idea how much weight it can hold, the water is still pretty cold, but I was able to stand on it without it breaking
The weak point will be the small amount of wood between the edge and the hole that the main bolts go through
Please let me know what you think, and if you have any suggestions!