Good comments -

Think the A class rule reads to the effect that no part of the boards or rudders can extend beyond the 7.5 ft beam limitation ,-in effect -no canted boards or foils.

The A s {a limited development class}- are the ideal small cat and hope they maintain that goal ,-the design measurement rule has produced beautifull refined cat designs .
good recent example http://www.morrellimelvin.com/sailboats.html

An ideal lifting design would have much larger overall beam for stability -like the Aussie foiler -with approx. 75% beam to l ratio of hulls and equal L to B Ratio w foils .http://marine.bdg.com.au/spitfire12.html

A interesting promising speed sailing craft from the UK is
this one http://www.whbs.demon.co.uk/sr2/content_fr.htm

Most of these speed machines are proa types ,-their primary design function -to sail beyond 50 knots in one direction on smooth water .

The interesting aspects of Sail rocket are its canted sail
{providing lift } and its main hull configuration being full at the bow and stern with the center area being above the waterline .

This type of hull design applied to a cat configuration with retractable foils may be an area of design pursuit , the other key features being light weight .-large beam to L ratio ,-and canted sail plan .