Found this comment from Patrice Guenole (Gong boss) on Facebook regarding fuse size. He makes a case for larger stabs for more radical riding and powered foiling. “Instability can feel radical. Stability lets you actually ride radically”. Worth a read in my opinion:
" Above 
If you foil without a wing, you need less stab. Based on your skills and feeling, decrease it as much as you want.
If you foil with a wing, you need a bigger stab.
Why? Because the wing creates pressure on the foil, causing the nose to dive. This pressure increases with speed and with the angle of the foil.
If you ride a smaller stab with a wing, it feels like it works. But… Actually, you are producing the opposite of what you want. You are just creating instability.
The longitudinal stability, nose up/down, becomes really hard to handle. It gives you the feeling of being lively and radical.
At the same time, the rail-to-rail is not getting freer. It depends mostly on the span of the front wing.
So you lock the turning ability and you unlock the straight-line stability.
The positive point that makes people think it is better in turns to have a smaller stab is that the nose up/down instability is also a way to free the turning radius when you have a big mast angle in the water.
But… because this angle is unstable, you can’t push as much as you want without making a mistake.
As we say, you have the illusion of shredding when you are actually riding “on eggs”.
For example, the best strapless surf foil setup for Malo is:
FW Fluid XS
Stab Veloce DW L
0° angle.
In addition:
The key point is to separate pitch stability from roll freedom. A foil does not only need to turn. It also needs to remain balanced longitudinally around its pitch axis. The front wing produces lift, but it also produces a pitching moment. Depending on the profile, angle of attack, speed, and position of the centre of pressure, this moment tends to rotate the foil around the pitch axis. The stab exists largely to balance this moment and to create longitudinal stability.
In simplified terms, the pitching equilibrium of the foil can be written as:
M front wing + M stab + M rig + M rider = 0
The stab contributes through both its aerodynamic force and its lever arm behind the front wing:
M stab = F stab × lever arm
This is extremely important because a relatively small force at the stab can generate a large stabilising moment due to this lever arm.
The force generated by any foil surface is approximately:
F = 1/2 × rho × V² × S × Cl
So the loads increase with the square of the speed. This means that when speed increases, the pitching moments increase very quickly too.
Without a wing or kite, the system is relatively simple. The rider, board and foil are mostly interacting with each other, without a large external pulling force acting high above the foil.
In this case, you can reduce the stab much more. This is why a small or low-lift stab can feel so natural in downwind. When you accelerate down a bump, a large stab creates more force as speed increases. If this force produces too much nose-up moment, the board wants to climb. You then have to push harder on the front foot, control the pitch, and sometimes pump to keep the foil moving along the right trajectory. With a low-lift stab such as an Hypertrail, the foil is allowed to keep moving forward with much less correction. The glide feels more natural because acceleration is not immediately transformed into excessive nose-up movement.
With a wing or a lowkite, the mechanical situation changes completely. The rig creates an external force. This force acts through the rider and is applied far above the foil. Because of this distance, even a moderate pulling force creates a significant pitching moment:
M rig = F rig × lever arm
The vertical distance between the foil and the point where the rig force is transmitted through the rider is very large compared with the dimensions of the foil itself. So the rig has a very strong influence on pitch balance. As the rig loads up, and especially as speed increases, this additional pitching moment has to be balanced by the foil system. This is why a bigger or more effective stab can become necessary. The mistake is to think that reducing stab size automatically makes the foil more radical.
What it mainly does is reduce pitch stability. A smaller stab generates less restoring moment when the foil changes angle. So a small change in front-foot or back-foot pressure creates a larger change in pitch. This feels immediately lively. The foil seems freer and more reactive. But a large part of this sensation is simply reduced longitudinal stability.
At the same time, reducing stab size does not free the rail-to-rail behaviour in the same proportion. Roll behaviour depends much more on the span of the front wing. A wide front wing has its lifting surfaces far away from the roll axis. These outer sections create strong hydrodynamic moments because of their large lever arm.
In simplified form:
M roll = F × distance from the roll axis
The greater the span, the greater this lever arm. This is why a large-span front wing naturally resists roll more than a compact front wing. So if you keep a large-span front wing and simply reduce the stab, you mostly free the pitch axis. You do not free the roll axis nearly as much. The result is a foil that feels unstable longitudinally without necessarily becoming much freer rail-to-rail.
This is exactly why a small stab can create the illusion of greater manoeuvrability.
There is, however, one real effect that explains why riders often feel that a smaller stab helps to tighten turns. When the foil is strongly banked, with a large mast angle in the water, pitch movement also contributes to the three-dimensional curvature of the foil’s trajectory. If pitch is very free, the rider can change the front wing angle very quickly. This can help tighten the turn radius. So the sensation is real. But the problem is that the pitch angle is less stable. The rider can create a very sharp movement, but cannot necessarily load that movement as hard or as precisely.
The foil becomes easier to disturb.
So there is a major difference between a foil that reacts quickly because it is unstable and a foil that can be pushed very hard while remaining controlled. This is why more pitch stability can actually allow more radical riding. The Malo example shows this very clearly. The Fluid XS is very compact and has a small span. This already gives him a lot of roll freedom and rail-to-rail ability. There is therefore no need to create extra pitch instability to make the foil feel radical. The larger Veloce DW stab gives him enough longitudinal stability to push extremely hard without losing control of the pitch axis. So the front wing gives him freedom in roll, while the stab gives him stability in pitch. That combination allows him to push harder, hold more pressure, and keep the foil exactly on the intended trajectory.
This is the important distinction:
Instability can feel radical. Stability lets you actually ride radically."
