As @ttokoro already noticed - minimize is quite sensible with respect to the initial guess value.
You may also use the root of the derivative and you don't even need to use symbolic calculation if you use the "root" function ("root" function with a provided guess value or a solve block with "find" would be other numeric ways to determine the desired position).
As you can see, using the derivative and the "root" function returns a result which is slightly more accurate (the corresponding H-value is slightly smaller).
Here is even another way to skin this cat, but I won't recommend it.
First we create vectors for u- and corresponding H-values and then use the "min" function to determine the smallest H-value. Lookup then gives us the corresponding velocity value.
