Dave,
The wording of the rules doesnt specifically prohibit gybing boards, but if you read between the lines, you can guess that they are not in the spirit of the F18 ruleset.

The line "being in the vertical plan (plane?) of the hulls" and "appendages must be symmetical." would indicate that they are not in the spirit of the rule. But you could always argue that point.

And you can make canted hulls from the same mold as long as you add a wedge to the beam socket on the inside halve, or fill it in later with goo. Being a production boat they probably have two differient molds, but its not a requirement.

Bill