Hola... long time no see! (or talk, chat, ?) 8)
Check these out... had one on a fish-and-ski back in my childhood days:
Or check out the whaler project on Classicmako, courtesy of Mr. Raybo. He just mounted a semi-permanent towbar.
As far as a leaning post, may I suggest something like this:
I have found that the swingseats, while versatile, are not as substantial offshore when you actually need to "lean" on them. Good luck!