In the smaller ranges HP competes with trimarans which are downsizing still.

The C40 corresponds to the Dragonfly 28. The latter stated weighs empty 2100 kg vs 800 kg for the C40. That must be based on different definitions.

A C36 would correspond to a Dragonfly 25, a Tricat 25 or an Astus 24, stated weighing in empty, respectively, 1150 kg, 750 kg and 850 kg.

I visited all these models. Being 6' even the Dragonfly 28 feels quite cramped beyond standing close to the companionway. What is the headroom in the galley of the C40? 

The Dragonfly and the Tricat with their swing wing floats add length when berthing up to half of what a HP lw hull would. Dragonfly does not offer a smaller model than the 25 whereas Tricat has a 20 footer.

The Astus has sliding beams limiting the inside useful length of the main hull just like the beams do in the HP ww hull. They have smaller models but I doubt they will develop a larger boat than the 24.

The Farrier 22 production model would correspond to a C32 and weighs in bare at 590 kg.

To what smaller sizes is this HP body plan still worth it?  C36, C32 ?