I`ve read all 7 pages..
I think Macca is trying to say that a stiffer platform is a good thing.
I think Wouter is trying to say that he`s right, but that no-one would double the cost of the boat to get a 2% gain.
I think they`re both right.
Doesn`t the F16 class rules stipulate the boat can`t be glued (ie must be take-apart-able for transport?) I think this sorts out the arms race a bit.

In the quest for ever-diminishing returns :
The Viper seems to have proved (by their results) that higher volume hulls (for 2-up sailing) is beneficial over smaller volume. Of course they must have put the volume in the right places as well.
Now they NEED bigger beams to stiffen a platform which has higher volume hulls, when compared to a boat with lower volume hulls.(This is independent of hull weight, since higher volume boats will be subjected to higher loads.) The bigger beams make the boat heavier once again. So the cycle repeats itself until the boat arrives at it`s weight (which in many folks opinion is way too heavy), but is still as fast as the lightest boats, meaning that the trade-offs seem to have worked slightly in their favour. (I say slightly as they have a highly developed rig and top sailors on their boats, which also gives them an edge).
This is EXACTLY what the F16 class rules are there for, and they seem to be working - Equalising boats that are built differently, but fitting into a boxrule.
If there were NO rules, Playstation would have won the F16 intergalactic champs, as they have taken the above to the other extreme. Bigger truck needs a bigger engine to make it go. Right, the engine is so big it made the truck heavier. "Frank, we need a bigger engine for the now heavier truck." Ok, but the truck will have to be bigger to take the new engine Oh wait...

Now for the case of ever INCREASING returns.
I have no doubt that Darren Bundock on a min. weight Viper would be faster than Darren Bundock on a standard Viper, and the min. weight Viper would cost a LOT more to produce. I won`t argue with Mr. Goodall on this since he seems to have built a boat or two.
If the hulls were built down to 15kg each, they would require a smaller set of (full-carbon) beams, so lighter hulls would require lighter beams, and the whole boat could be built to min. weight, or even 20kg lower, quite easily, if enough money were thrown at it. Min. weight mast with super-light sails that last a regatta or two will help.
Would this cost more than a standard F16 design ?
I think that`s what Macca and Tornado Alive have been trying to say all along. (But I`m not sure).