Retrofitting stabilizers on your motor yacht contrary to popular belief is actually quite simple with the Gyro-Gale brand.
The stabilizer fin mounting plates are installed with through-hull bolts. The large surface area of the two plates when squeezed together against the hull create a very strong bond which does not require any fiberglass blocking or reinforcement.
After the plates are installed and a few additional steps, the boat is ready to splash!
Check out how a Gyro-Gale system being installed: