Your design—which utilizes submerged buoyancy foils connected via minimal struts to an above-water living structure—is indeed fundamentally a SWATH (Small Waterplane Area Twin Hull) vessel, though yours is a "tri-hull" (or SWATH-tri), which is an interesting and potentially advantageous twist.
SWATH designs are brilliant in concept but notoriously difficult to execute. Below is an overview of SWATH successes, why they aren't the standard, and the critical lessons you must apply to your seastead design.
SWATHs are not common, but where they have been used, they are highly valued for one specific reason: exceptional seakeeping in rough seas. Because the waterplane area (the intersection of the vessel with the surface) is tiny, the vessel is virtually immune to heaving and rolling from waves.
Despite the smooth ride, SWATHs remain rare due to a cascade of engineering and operational challenges:
Your specific design introduces brilliant innovations (the 3rd hull, the NACA foil shape, the active stabilizers), but it also inherits the classic SWATH vulnerabilities. Here is how the lessons of past SWATHs should guide your engineering:
You mentioned the bottom of the legs are sloped at 5 degrees to provide lift at "very high speeds." This is extremely dangerous in a SWATH design. If a SWATH generates dynamic lift, it rises out of the water. Because the struts are thin, as the vessel rises, it loses waterplane area rapidly. This creates a positive feedback loop: the vessel rises, loses stability, rises more, and eventually broaches or flipping sideways. SWATHs must be drag-biased, not lift-biased. Traditional SWATHs actually add centerboards or fins specifically to create downward force at speed to keep the struts submerged. If you want to go fast, you must rely on your "little airplane" stabilizers to manage pitch, not the hull's bottom slope.
Your design has the legs 50% submerged. If you load the seastead with more people, water, supplies, or solar equipment, the struts will sink lower. Because your struts are 19 ft tall, a change in weight could easily submerge them entirely, at which point you lose your SWATH advantage, drag increases, and the structure sits dangerously low.
Guidance: You must incorporate active buoyancy compensation. Your NACA foils should have internal ballast tanks or air-compression chambers to actively manage the 50% draft as payload changes. The 3-leg design helps distribute weight, but you must mathematically model the center of gravity and center of buoyancy for every possible load scenario.
Most SWATHs are twin-hull, which makes them prone to roll if weight shifts laterally. Your 3-hull (trimaran-style) layout is actually a massive improvement for static roll stability. However, you must be careful of wave interference.
Guidance: The front leg will create a wake. Depending on your speed, that wake will hit the back two legs. At certain "hump speeds," this wave interference can cause severe drag spikes or structural resonance. Your RIM drive thrusters should be programmed to avoid continuous operation at these resonance speeds.
Your NACA 0030 legs with a 10ft chord and 3ft width (30% thickness ratio) will provide excellent buoyancy and structural depth. However, the junction where the legs meet the 7-foot-high triangular truss will experience massive bending forces, especially if a wave hits the top structure (windage) while the bottom is anchored in the water.
Guidance: The connection point between the legs and the truss must be heavily reinforced with fairings to reduce stress concentrations. The truss must be rigid enough to act as a bridge connecting the three legs without flexing.
Your "little airplane" stabilizers with actuators are the most forward-thinking part of your design. SWATHs have low natural frequencies for pitch and roll, meaning they move slowly, which is perfect for active control systems.
Guidance: The stabilizers must be controlled by an active IMU (Inertial Measurement Unit) system. If a wave pushes the bow down, the forward stabilizer must instantly deflect to push it back up. Also, ensure the pivot point of your little airplane is precisely at the center of lift. Your 25% chord notch idea is aerodynamically sound (it prevents the actuator from fighting hydrodynamic torque), but test it in CFD to ensure the flow over the notch doesn't stall the elevator at high speeds.
A 70ft wide triangle with "lots of glass" will act like a massive sail. In crosswinds, the seastead will drift sideways rapidly because the waterplane area is too small to resist lateral movement.
Guidance: Your 6 RIM drives (1.5ft diameter) are a great choice for low-speed maneuvering and station-keeping, but they must have enough aggregate thrust to counteract the windage of the superstructure. You may need to implement a dynamic positioning (DP) system tied to a GPS/Compass so the thrusters automatically fire to keep the seastead on heading when wind pushes it.
You stated "the blunt or leading edge... facing forward." In a NACA 0030, the "30" means 30% thickness ratio. It has a rounded leading edge and a tapered trailing edge. Ensure you are placing the rounded edge forward (which is the correct, low-drag orientation). Placing the blunt/tapered trailing edge forward would cause massive flow separation and drag, completely defeating the foil shape.
Your design successfully captures the primary benefit of SWATHs—a smooth, soft ride in rough water—while cleverly solving traditional SWATH roll issues with a 3-point hull. However, to avoid joining the long list of failed SWATH projects, you must absolutely prioritize strict weight/draft management, ensure the structural rigidity of the struts, and prevent dynamic lift at high speeds. If you treat the vessel as a strictly displacement-mode platform stabilized by your active foils, you will have a highly capable seastead.