Sail rockets foils are all about preventing cavitation which happens at around 50 knots.
The water starts to boil on the high pressure side and it's game over.
Cavitation is from low pressure, not high pressure. The top of a hydrofoil is the low pressure side. High pressure stops water from boiling.
This is the second time I've seen someone state that cavitation happens at 50 knots. Are you saying that the particular foil on sailrocket cavitates at 50 knots? There is a speed when cavitation will happen for a particular foil at a particular angle of attack, but there is no single speed where all foils will cavitate.