RE: North Sails "One mast fits all" concept.
We have communicated.
I see your points very clearly, and since I'm also a smaller lightweight sailor, I too must "experiment" with softer masts to get the most from my sails.
Experimenting with alternate masts is good, after you've tried your sail on the recommended "best" mast to find out what the designer had in mind.
I've never said that the North "Extendo" system does not work. I'm sure that it does, and there are thousands of sailors using the 2 mast concept with good success.
But I, like you, have a bit of trouble seeing how you can get the optimum design performance with the 2 mast system, throughout a wide range of sizes, unless whoever designed the sails also used the "2 mast system" in their designs.
It seems pretty clear to me that in the case of the sails we are discussing here (and nearly all sails in general) that the sails were designed on a specific mast.
It would be very cool if the sail designers would also give us some of their "design parameters" like how heavy was the sailor they designed and tested the sail for?
What actual windspeeds did they focus on for a particular size sail, and did they test outside that range?
The "best mast" and the suggested rigging parameters are nearly always the best place to start, and then we "customize" (your term) to make the design work for us.
Hope this helps,