Those are also tiny little things covered with branches (read: knots).
I shudder at the thought of how many pieces you would have to scarf
together to make anything useable.

Well...a lot of them are. I have 3 acres on Harding lake where the average
diameter is maybe 6 inches, exactly as you describe.

There are some areas, though where the growth is not so dense, and they grow
bigger. I know many stands of 2 foot diameter trees (3 in my front yard)
where the bottom 20ft or so look like they might yield a spar or 2 if cut
carefully.

They still don't get VERY big though. I wonder how big they need to be to
yield a proper spar.