Searched and searched but didn't see a post on a swing out mount like the ones on the Harbor 20. Probably wasn't holding my mouth right. Maybe the Slocum approach to an auxiliary is the way to go. I certainly enjoy his company anyway.
Ebb, I suppose if using the outboard hole as a large scupper one could put a large flapper valve in the small access behind the rudder post to prevent back flow. Do you think back flow would be a problem in heavy following seas? I had a Cal 20 with the outboard well in the floor of the cockpit and always expected more slosh than I ever really got. Funny story about that Cal 20 if anybody is interested.
This may seem a bit heretical, but after sailing "Sinbin" upwind from Angel Island to Fortman Basin against a front, I decided I was sick of bailing. So, we sealed the plug with Sika flex, beefed up the transom from the inside with glass and plywood backing plates, bought an outboard bracket from West, and hung the outboard off the transom. That was in 1995. Three outboards and a standing rigging later, "Sinbin's" transom is still intact. Down below, she is dry as a bone.