The majority of modern high performance boards and "everyday" performance boards these days come with the 5 fin option. Seems that the standard modern thruster has a single concave, into a double through the fins, and usually some sort of V. I would guess 90% of pros on tour are riding that setup, 100% of the time. (With the exception of Toledo and Slater lately). If these same boards were designed purely as quads, how might the shaper change the bottom contours/ Vee (in the rear half of the board) to make it work best with 4 fins ?

And while we're at it... should the shaper keep the front fins in the exact same location as the tri board ?

On a slightly different topic... you hardly ever see single concave performance boards anymore. Does the longer/ narrow outline of short boards have enough drive already in them , that the goal is almost always to loosen the tail up? Did/do guys like Occy/ Sunny/ Pancho, or modern heavy footed carving surfers like Wade Carmichael, ever ride single concave ? One of my favorite boards ever was a 5'8 Dumpster Diver (with a really curvy outline at 19.75 wide and pointed nose) which was a single concave model.

Just wanted to open up a little discussion to nerd-out on board design, and hear some thoughts.

(What I liked about the dumpster diver best was the ability to really hold a rail, powerful cutbacks, while still feeling just loose enough to get the fins free)

Sometimes shortboards, which I ride in the 6' x 19.75" range, feel great until I get vertical, and they're so damn loose and squirrelly, feel like the boards want to do nothing but airs and fin drifts, or above the lip stuff, when I just want to bury a rail and soak my buddy.

Trying to dial-in my next custom orders. Thanks for any input / shared knowledge.

Another thought... instead of changing the concaves from single-double-V (when making a board ad a quad), might just switching the tail shape to something like a swallow or baby swallow be more effective than changing bottoms ? (A-la Felipe Toledo)

You really need to try a legit bonzer. The hold in big waves is amazing. Super fast tick racking but carving from rail to rail transfers is fluid and smooth. The concaves are not easy to place or shape. Bing, Campbell brothers and Larry Mayo seem to have it down. They are not, in my opinion, meant for small waves. My 7'4" Bing synchronizer is what I use in anything more than overhead. I've had this board in triple overhead and still had the confidence to drop in fast and angled and slot myself as best I can. It's the only board I have ever had that kind of confidence in. The slots and concaves seem to be the difference. But also the widely placed side bites and their angles. It's all an alignment of things that work very well in the perfect proportions.

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"One of the reasons why propaganda tries to get you to hate government is because it's the one existing institution in which people can participate to some extent and constrain tyrannical unaccountable power." Noam Chomsky.

There is a huge variety when it comes to five fin set-up and I don't think any two are really the same, unless they are copies of each other. Personally, I like thrusters in little waves because they are easier to control, quicker off the mark and fit into tighter spaces, whereas quads feel better under my feet in larger waves were there are open faces, drawn out lines and space to add some soul to my surfing. Of course there are exceptions, Techo, a local shaper in Satty, has the quad thing down and his boards are a good hybrid of the two; tight in little stuff and grippy and flowing in size.

As I recall, the old single concaves were derived by the need to flatten out a constant rockered blank. Some of my original thrusters in the early to mid 80's were slow as mud till that was figured out and even then it was a game of details, too much concave into the tail rocker and the board would lift to the point on no control, too little and it was back to mud surfing.

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I was right.