I have made a couple that resemble the Björn Thomasson drawings. It is a great paddle. I use the ridged face as the power face. The ridge provides the dihedral that splits the water flow and prevents flutter AND puts the effort point on the blade forward of the loom stabilizing the stroke. It sucks for rolling and sculling. A Greenland paddle is still a more versatil paddle.
There is a lot of contoversy over which face is the power face with many theories. The Italian web site has an Aleut paddle with a quite convex "back side". Coupled with a minimal ridge that could be used more like a GP. I have one of that type in the works and I think it will be very different from the flatter ones. It's fun to experiment with these as there is so little info on them.
: I built one from the drawings in Brinck's book. The shape means that the
: centre of effort (where you put the force into the loom) is behind the centre
: of resistance (where the paddle blade pushes the water) which makes the
: paddle
: very badly behaved - a huge amount of flutter. This put me off building or
: trying to use traditional paddles for quite some time. Eventually I carved a
: GP, and this is much better (except that eventually, it has warped a bit )-:
: I note that the diagrams that have just been posted seem to show the blade
: face being somewhat convex. With my background of using Euro paddles, I
: carved
: the power face of my Aleutian paddle very slightly concave - maybe this is
: part of the problem ...

: Mine was laminated from two pieces of spruce - there's one little knot in
: one blade face, but, as I recall, the laminated piece is behind this, so it
: doesn't go right through... The GP was cedar with two strips of ash laminated
: either side to make the loom - it has a much nicer feel.

: Andy