I finally did it. Full circle, 360 degrees.
As usual, vertical paddle, reach out, etc.
What was different (and I was on ULI Lopez 10 ft 29 inches, 3 fins, in absolutely flat water), I stepped a bit back and buried my right rail all the way, with my left foot on opposite rail, way in the air (the feeling is that a bit more and I put my board on the rail). And thats all - 100 or so strokes on one side and I came more or less back.
And then I did it on the other side (a bit less efficient though, i am not completely symmetrical, i guess).
I then played with less rail, and I can go straight unlimited number of strokes. Simple and amazing. Have no idea if it will work with another board.