Hey Andrew,
I ran into a problem with my hydrofoil because the 1/x type function does not model the v^2 term of the lift equation correctly. The steeper slope decreasing the servo deflection should be at the higher throttle or speed instead of lower.
Should be the blue line shape and not the orange
But also, what you mentioned about the calculation does appear correct to me. As with my issue, it would appear that there are a lot of small mistakes in the speed scaling that are being masked by forgiving planes and PID loops!