Thanks azymuth, means a lot coming from you

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That's the first I've seen of Frank's. Looks solid.
Mine are essentially a ball (cleat) retained by a pin connected via 2 Stainless steel extension springs. The upper radius of the cleat profile matches the pin diameter to lock in place. The lower taper angle of the cleat allows for lower force required to engage VS the force required to break away. The adjustment screw increases the spring pre load. I designed mine to break away at a given force regardless of the direction force. For example, my worst crashes are when the board rolls to leward and I fall to windward, so not just in a forward catapult direction, but any direction.
My design criteria was...
1. keep the stack height as short as possible with smooth curves to not feel anything but the straps
as I'm usually bare foot.
2. All stainless steel and UV stabilized composite materials.
3. Self clearing/flushing of debris.
4. Re-engage the cleat by foot while slogging (takes some practice though). Not really relevant if you have to water start though.
I'll post some more details/video when I get a chance.