Will,
I think this post belongs in the Tornado mast thread. But anyway, picking out an aluminum mast to suit a team's wants/needs, assuming such a mast exists, is a matter of going to the boat source and testing several masts from the mast storage rack. You do not have to buy several masts to pick out a stiffer one or a softer one to suit your wants/needs.
Your next comment about the carbon mast confuses me. You start off saying a team can have a carbon mast built like you want/need. Then you go on to say its quality can be tightly controlled. If a carbon mast is built to each customers needs, every mast is a different composite layup. On the other hand if the quality is tightly controlled, all masts are identical in layup, weight, section, bend characteristic, CG location,etc..
The other part of your post has to do with narrower and lighter which I think is a spin off from the SC17 pitchpole question. I'm lost.
Your comment about, "on lighter weight boats the crew becomes a greater percentage of the total package weight and has more control" over everything, total sailing weight and max righting moment, is very true. Boat weight plus crew weight equals total weight. Total weight is the prime driver of hull drag. Lighter weight boats become righting moment limited in less wind strength and require crews to trapeze sooner. Max righting moment determines max sail thrust sailing upwind especially. The two most important drivers of the speed of a particular sailboat design are HULL DRAG and SAIL THRUST. On a lighter weight sailing system the crew weight affects both hull drag and the sail thrust to a greater percentage than on a heavier boat. The lighter weight sailing system will be more sensitive to variations in crew weight than a heavier weight boat. This is an inherent undesireable characteristic of lighter weight boats/platforms.
Bill