I have the opportunity to buy a used Naiad 302 Stabilizer system with 12 Sq-Ft fins. I would install them on a Symbol 57 Pilothouse. I will only go displacement speeds 99% of the time, so I think bigger is better. I have a call into Naiad, but thought I would throw it out here first.
It’s probably not an issue at slower speeds, and really slow (<6 kts) perhaps an advantage. The biggest issue is with planing boat where at speed very little fin is required to stabilize, and drag goes up by the cube of speed.
My only concern would be when you are at full speed. Would the stresses on the hull be too great? I have a 63’ motor yacht and my fins are 9 sq ft. They are more than adequate at hull speed and don’t seem to be an issue on plane at 18kts.
Contacting Naiad is the right thing to do. You might want to contact Symbol about the layup schedule in the area where they will be installed.