I neglected to mention in my original post that I bought (air-dried) bending oak for the ribs.

I decided to go with the Doug Fir that I have and started ripping it to size last night. It really is fine wood. It planes well - it doesn't throw off ribbons quite as nice as pine would, but there was no splintering or shredding. Cunningham recommends 7/8" thick gunwales, but as per some of your recommendations I'll take it down to 3/4".

BTW (see my post of a week or so ago) I bolted a 12"x18" plywood base to my HD Porter-Cable circular saw (as per Cunningham's recommendation; I don't have a table saw) and am using fences clamped to the plywood base for ripping the gunwales. As a modestly skilled wood-worker I was a little nervous about modifying and using the circular saw this way, but I'm just amazed at how well it works and at how safe the setup is. I even used it to cut some small pieces for the Nystrom-inspired rib-bending jig and they're just perfect. After so many years of indifferent, not-quite-parallel cuts it's so cool to finally be doing it well.