Tim,

Info about costs can be found in the excel sheet I linked to earlier.

With respect to your other points.

About halve a year ago it was discussed how the F12's could be stacked on top of eachother on this public forum, mostly because the masts come of so easily. A portion of the group is working on deep V-ed hulls that will allow a metal strip to be fitted to the keel. These boats be dragged over almost any surface (boat ramp ?) and can be stacked on top of eachother without any need for a rack. Transport will be much the same. The necessity to store these boats stacked was identified early on (last year) as an another beneficial quality the F12's should have. The deep V-ed hullshape also makes the keel line strong and robust under abuse.

Windsurfer masts.
I'm actually the one with Grob who has been experimenting with windsurfer masts in this role. My first impression is that this route has a few issues that are not easy to solve. The Blade 12 will suffer more in this respect as its pod design is less suited to keeping an unstayed windsurfer rig upright. The push rod setup as shown in the pics of the alternative F12's is better suited to taking a windsurfer mast but the issue of these masts being to flexible (pumping) is not totally negated by it. A seperate metal tube reaching higher up the mast externally (as Grob uses succesfully) is needed, however if you are going to use a bottom alu section to support the windsurfer mast anyway, why not go for a full metal tube mast. The top sections are not the problem, neither in weight or cost.

Also I don't think the F12's need many different sailsizes. One of the bettter aspecst of a catamaran is that these carry large sailarea's rather well without losing control even in big wind. I think we can do well with only 1 sail size or at max 2.

Apart from the hulls, the sail and rudders all other parts are very easily home-made by an amateur. The alu tubing mast costs 260 euro's commercially (it is basically a class 5 landyachting mast) and for that price I wouldn't go through the trouble of making one myself. The rudders can be scavaged of any other catamaran design like an old hobie or prindle. These being oversized is actually an advantage. Otherwise a new set of Dotan rudders will do fine. The sail can be homemade or sources from a local supplier. It is my intent to publize a decent sail design free of charge so everybody can build it himself or have a local sailmaker make it for him. Even when these three items are bought new commercially then the total costs aren't expect to pass 3000 Euro's overall. (see the excel sheet).

I feel that Blade 12 by Phill will be very much along the same lines as the F12's in this respect.

Wouter