In the end, it's really about cost isn't it? Or at least, the PERCEPTION of cost. By going OD on a lot of the boat elements, conceivably an entry level team could spend less on getting into the event. By having more of the design open to development, that's more money and time to spend on developing the boat, more need to have multiple boats, and more need to have large crews to sail and man them all. The OD wrinkle was added to try and get the costs down so more competitors would sign up.

A-cats have a pretty basic set of design rules. It literally fits on one sheet of paper with the exception of the interpretations. They're available here: http://www.a-cat.org/sites/default/files/ISAF%20A%20CAT%20rules%202010_0_0.pdf

Rule #8 was added in order to limit foiling and it specifies a minimum "tip distance" for the daggerboards in a down position from the centerline of the boat (to limit the horizontal section of the foil) and that the boards must be inserted from the top of the deck. It does not limit the dimension of the board in any way other than those two parameters. If you build a board that's too thick or too long, you eat a drag penalty. Two short or too narrow and you don't get enough side bite or lift.

The rule works, mostly, but I think the guys figured out work-arounds faster than imagined. I would argue that the rules now making foiling difficult, but not impossible, but still pretty impractical for the common person sailing in the normal conditions. They've essentially straddle the fence with the rule and perhaps it was the right call. A-cat participation isn't terrible but practically none of the foiling guys show up to our lake regattas anymore (the conditions are not very likely to suit them) and I would argue that more than before choose to avoid events based on the forecast conditions. On the other hand, a full on foiling rule set would have made an entire foiling switch for the class and probably caused a lot of a-cat sailors to cut bait. Or a tighter rule making foiling all but impossible might have driven guys with money and time to other classes where they could foil. All decisions would carry some sort of damage to the class and I think all options were not great but that the class choose the better path.

At any rate, my point is that the a-cat class has a very short and very simple rule set - and it works. However, we also don't have billionaires in the ranks and the equipment war has been kept somewhat to a minimum just by cost and the free resources of the people that currently participate. You will spend a good deal of money to live at the pointy end of the fleet but you can also have a good result with an older non-foiling boat if the conditions are reasonably mild. Personally, I love sailing the boat...it's incredibly responsive and easy to handle/maneuver. I got back into A-cat even though everyone else is foiling just because it's a great way to spend an afternoon on the water.