Some thoughts on what's going through my head at present (while I wait for answers to the questions I sent the GC) for interested parties:

As most of you know there has been a discussion on the main forum about "Better cat design" and one of the main points that most seem to agree on is the need for more volume (as seen on the Infusion in F18 and Aussie Blade in F16), however, the A cats have been going in the opposite direction for quite a while. I believe this divergance is for two reasons.

The addition of a spinnaker and its added horsepower has seen modern designs focussing on making it easier to harness this power rather than efficiency. So we've maybe given up 1 or 2% top end speed in order to make it possible to sail the boat flat out 95% of the time rather than 85% of the time.

The other main difference is the displacement length ratio of the hulls. Using Dimensionless values these are:

F18 : 1.96 (crew weight 150kg)
F16 : 1.90 (2 up crew weight 130kg)
F16 : 1.47 (1 up crew weight 80kg)
A Cat : 0.94 (crew weight 80kg)

Of interest here is the F16 two up and F18 have very similar values, which is resulting in these boats converging on a similar "Max volume" philosophy.

The A Cat is much lower (50%) and as a result can achieve different targets and performance, which is why a lot of A cat concepts and shapes can't be translated straight into F16 and 18.

As mentioned before, my boat is being designed as a one up boat only which gives it a disp/length ratio smack bang in the middle. So the first thought becomes "ok will A cat shapes now work?" and then how much volume do I want and where. Needless to say the computer is getting sick of running models.