RE: severne sails tack pully?
I have been using Bill Hansen's sails (Windwings) for over 20 years, and he started using a sewn-in 3 position fairlead in the early 90s and changed more recently to a 3 sheave/pulley design. While I matched the sails up with Fiberspar mast extensions, I believe they are the same in concept as the NPs. The combination yields sail and base axes at 90 degrees to each other. I should point out that I always rig with the starboard side of the sail up, so this must be kept in mind when following the instruction below.
To successfully thread the line and avoid any crossed lines, there is only one way I found that allows a virtual mating of the sail to the base. Starting with the tie off point you thread the line up and over the sail sheave closest to the mast and down and through the top of the base sheave closest to the cleat. The line should then be run up and over the frontside of the sail sheave farthest from the mast so the line comes down and enters the base sheave closest to the tie off point from the bottom. The line then comes up and runs through the middle sail sheave from the underside so that the line ultimately comes down and threads through the cleat. The secret is that the line is worked around the sheaves in opposing directions.
More recently I bought another brand mast base that included the Streamline "Quick 6" pulley system where, as you pointed out above, the sail and base axes align. Unknowingly, I tried the opposing threading method I had been using for years. Big mistake. While I ultimately figured out the proper method, I still fought with it a number of times before getting the picture.