We have replaced dozens of them in the dealerships, total carp and that's from a VP mechanic, they have cheap nasty gear mechanisms that break if they get fouled, they have no effect until on the plane.
Give me good old Bennet flaps any day, they work from slow speeds and can definitely help a boat on the plane, mine which are original from 1987 still work perfectly on my classic Draco. All IMHO of course.
Not my taste. Changed them away from my SC35. Huge drag and totally worthless in slow speed and they not helping to get boat on plane. Also bow trimming is quite ineffective. Choose traditional ones if u can choose.