Thank you all for the clear and concise responses. They allow me to hone in and clarify my inquiry. Obviously dinghies & multi-hulls have different parameters for "surfing vs. planing", and to muddy the water, (sorry for the pun), there is now so much development in lifting foils, T-foils, hull shape and stability that our very basis for what is "hull speed" may not be so clear anymore. Good possibility I am wrong but I believe in the era of the age of sail up to and including the clipper ships, hull speed was determined to be the square of the weighted waterline length, as the twentieth century progressed it became 1.34 the square of the WWL. Love them or hate them, the America's Cup T-foilers WWL has absolutely nothing to do with hull speed, and they are in flat water. Obviously they are not surfing but are they really planing? Are they just an anomaly? Do we just sort them into a range of their own, (not dingy, not multi-hull, developmental?). The wakeboarding video's bring out a part of this. Notice the difference in the length of the different boards. In the 1st video the board on the outside is noticeably longer and the guy is just cruising, the others are shorter and obviously more responsive but kinda need to be "worked" to stay on the wake. Then you have the foiler who can go faster than the boat creating the wake, until he runs out of wake. When I'm at the helm of my boat I'm more like the guy with the long board, my younger crew are much more aggressive on the helm, knowledgeable pumping of the sails seems to help us all out equally.