I checked out the Hattori 3717. Love that design and I may eventually get one, but it's not exactly what I'm after. I like to be able to hold the knife as close to the cutting edge as possible. This works on a puukko with the edge ending against the wooden handle or metal bolster, but not on a knife where there is a lot of blade between the handle and the edge.
I like smaller blades with a decent choil, like the Spyderco Native 5, or medium sized blades (between 3" and 4.5") with the cutting edge ending right at the handle with zero unsharpened blade steel between the two. I like a slightly tapered blade, like a Kellam or Ahti puukko style knife, but prefer a wharncliffe style edge for working with wood. I also like the rat-tail tang thru wood handle style for this sort of things. I like the feel of a full-wood handle and the lightness and balance of a concealed tang knife. I have some Moras, a few Enzos, and a few Fallknivens. All great knives, but after using each pretty extensively I find that my usage style is best suited to a wharncliffe design with a totally straight, flat edge. If I want a blade with belly while I'm working, I typically reach for a different knife like my Native 5 or Enzo Trapper.
Incidentally, I've tried longer standard puukko style blades where there is 3 or more inches of straight, flat edge before the belly begins, but with a longer blade I find I don't use the belly at all, so any length the belly adds to the knife is wasted and often a hindrance.
I took a look at the Finnish Army Signal Corps knife. It certainly has the blade to handle relationship I'm looking for, but it looks pretty crude. I may save my pennies and get a forum member to make me one once I draw it up. I may also try to contact one of the puukko blade suppliers and see if they can simply sell me a puukko blade that has not been ground yet. A Kellam Puukko with the blade installed upside-down and with the spine sharpened rather than what is normally the edge side, would be just about perfect.
Thanks, all, for the info and suggestions. The Hattori sight is dangerous. I could spend a few days drooling over those knives.