Bob:

You might get away with doing something similar to what I described in a recent post here:

https://www.clcboats.com/forum/clcforum/thread/44040.html

...but, if I'm scaling things correctly from the Jimmy Skiff drawings, they'd need to be half again longer than what I did for my PMD.  They'd probably need to be stiffer, and therefore heavier, on account of the much increased span, and maybe the idea becomes less actractive.  At that length (maybe something a bit less than 4-1/2') they might get a little awkward to handle, too, hard to say.  Once you have all of your interior done, you could try it with a piece cut off from a stray 2x6 just to see, I guess.

If you mean to sail the boat seriously by yourself, you will want to do something if you don't want to sit on the bottom all the time.  If you sit on the stern seat, she'll be badly down by the stern.  Sitting astride the midship thwart might get awkward, too, though maybe not as bad as my PMD that way.  You might want a longer tiller to do that.

Hope that helps a little.

.....Michael

   Thanks this looks like a good idea to try and better than tring to build permenent stde seats.  I also have an Eastport pram that  could use a side the bsame seats

Have you looked at the seats they put in the Jimmy Skiff II?