I guess it has been a while since I have posted.  Some progress to report.  I managed to finish a wooden steam box - used the same design as the styrofoam try 4.  Works fine!  Temp gets up to about 205 - not quite as hot as the styrofoam box, but can be used more than once!

Last week I steamed removed, cleaned, steamed and installed 2 more ribs, these toward the center.  Then this week, did the same again, this time replacing 2 more toward the stern.  So, up to 5 ribs installed!  So far they seem to going in quite well, better than I expected.  All the prep, shaping of the ribs, etc. takes about 8 hours for 2 ribs, so that is about all I can do in a week.  None the less, at least I can see steady progress.

It was looking like the bottom was sagging a bit in the stern where the most damaged ribs are located.  I added another temporary 2X4 'keel', attaching it ahead and behind the damaged area.  This seems to pull the bottom up to flush and hopefully will keep the ribs in place until I get to replacing the bottom planking.

I think I am up to about 14 ribs that will need to be replaced - perhaps more.  I'll continue replacing them 2 at a time - looks like I'll need to shape a few more from the lumber we bought last winter.