Yeah, Bethwaite is heavy going at times! I have the older High Performance Sailing and recently bought Fast Handling Technique.
In HPS Chap 16, Quest for Speed, p. 185 Bethwaite details his research with a trimaran type format. Interestingly he says, “I had tried all the other hull platform and rig setups, and had concluded from bitter experience that this relatively conventional trimaran setup was superior in the practical world of real unsteady wind and often big waves to all of the others. It was practical, controllable and fast.”
He also mentions they are tremendous fun.
So something of a recommendation for the Weta style configuration.
Perhaps a short summary of FHT would be “loose the cleat”, i.e., in gusts, ease and squeeze.