RE: North Sails "One mast fits all" concept.
Roger phrases things nicely above. I would add that while its a sort of nice service to the customers on a tight budget to go the "1 (or 2) mast fits all" route, there is still a fundamental problem that smaller sails need softer masts to work to their fullest potential (and larger sails need stiffer masts). That is for example manifested in the 430 being the rec mast for the Daytona 5.4. Even if you specifically try to design a smaller sail to work on a stiffer (longer) mast you would have to do some compromises to get there and end up with a less responsive rig.
So, personally I think its is in most cases better to go for perfect fit masts, at least as a long term strategy. If you're getting a new quiver now, I would for example argue that its better invest in complemantary masts next time (instead of getting fresh sails again).