……It is entirely unclear to me that any prone method of wave-riding achieves the momentum changes common in competition shortboarding. It precisely the ability to move the board relative to the center of mass that allows standup surfing to achieve these momentum change advantages over kneeboarding, paipos, bodyboards, mats, and bodysurfers. Whereas standing is a disadvantage in a passive control system, it can be an advantage in an active one.
Virtually all high maneuverability vehicles (e.g aerobatic and fighter aircraft, race cars, etc. achieve that maneuverability through low moments of inertia–around the relevant axes–relative to the torques that can be generated). Planing type craft such as traditional surfboards, kneeboards, paipo boards, and bodyboards all have the characteristic that as the board is banked to carve (not skid) a turn, the center of effort on the bottom shifts laterally so as to resist the generation of the torque about the roll axis that is necessary to achieve the required bank. While this generates stability, it inhibits maneuverability (fighter aircraft being the epitome of this relationship as modern designs are so unstable that they must be controlled via a computer). Thus how much, and how quickly the board can be banked is limited by ergonomic factors: the separation between the heel and toe and the stance (or the need to change it) in the case of a stand-up surfer, the distance between the knees (or between a knee and one’s arm reach) and between the knees and toes (or tips of the swim fins) in the case of a kneeboarder, and how much (and how quickly) a bodyboarder can shift his center of mass laterally (and fore-and-aft).
The HYPO board is different in that there is an initial slight stability, but with just a little bank angle, that changes from stable to neutrally stable, and then with more banking, to unstable. Thus the hydrodynamics of the design assists, rather than resists, the generation of a torque around the roll axis (of course, at the same time it can require more skill on the part of the rider to achieve the desired bank without over- or undershooting–just as with an aerobatic aircraft). It is this feature, in combination with the low moment of inertia about the roll axis, and the substantially reduced induced drag in executing the turn due to the foil, that gives rise to the enhanced maneuverability (defined herein as the ability to quickly initiate a maneuver, execute the maneuver in minimal distance, carry speed through the maneuver, and quickly recover from the maneuver) of this design.
[However, I concede that in some instances a high moment of inertia could prove advantageous to someone who is reflex and balance challenged. ]
As far as contest surfing, I agree that a standing position may be advantageous to perform many of the maneuvers that are (or need to be) executed to gain points. However, I also find that many of those maneuvers–while demonstrating high levels of skill with regard to balance and reflexes, and which can involve considerable risk of failure (e.g. snapback, fall on your back on the face of the wave, skid along on the face of the wave on your back with feet still on board, pull yourself back on the board with your legs, then recover and stand back up)–really don’t appeal to me. And from what I have read in interviews, I gather that this is even true among some of the contestants as well. In many ways it seems like the goal is to chop up the meat (wave) into hamburger rather than carving it up in accordance with it’s natural evolving form (form follows function → no form, no function