Mark, clearly I am interested in this subject even if we are boring everyone else. A couple of points though:

1) My boat is a bit more than 6.5’ from fair body to sheer, eyeballing an average (over 8’ above fair body keel at the bow, about 6.4’ at the lowest shear point). So one might estimate 700 sq ft for the sides. However the CAD surface area of the whole hull fair body is only 867 sq ft, excluding transom and keel stub. A cat has narrow waterlines and there wouldn’t be as much “bottom”. The flat deck areas which might be surrogate for the “bottom” total to 461 sq ft. on my boat. So freeboard x length may not be a close enough estimate for our purposes

2) I think you may be off a little on your laminate thicknesses. If the outside skin where really 1/4” and inside 1/8” with 1/2” core, the unfinished laminate would weigh about 3.3 lbs/sq ft. If the Alpha are constructed that way AND had twice the area of my boat, the laminate alone would weigh nearly 18,000 lbs vs. its 9.5 ton claimed displacement (now we don’t know if these are short or long tons, and I have often stated my low confidence in manufacturers claimed displacements). However I think the skins may in fact be lighter. On my boat test panels were measured: inside laminate was 35 oz hand lay up measuring 0.090” and outside was 70 oz vacuum bagged measured at 0.120”. I made the outside skin twice as thick as engineering required due to concerns about susceptibility to local damage. If the Alpha used your example glass weights and was bagged, the laminate would probably weight more like 8000 lbs. I discovered a surprising amount of weight is in the tabbing and reinforcing for a composite interior beyond the raw areas - I had to do some forensics when I weighed my completed composite structure - not correctly estimated by the NA.

3) My boat is mostly cored with 1”, not 1/2” core, and so has twice the flotation in the same laminate.

4) Mine is not a particularly beamy boat in modern terms at 13.5’. The Alpha is 24.2’ so something less than 2x beam.

I still think it would sink without a LOT of permanently watertight compartments. I would like to know if the Alpha was actually weighed in cruising trim. One thing that CE certification has done to European boats, they are more honest now about displacements - they are required to be.