Mine are mounted very close to the widest part of the boat. It lines up with the 2nd screw from the front of of forward window. It's been there for ages and I doubt any science was applied to the positioning.

:: Getting the new boat ready for our first Wednesday
:: nighter and I'm wondering where the best place to put
:: the twings on the rail - just aft of the shrouds or
:: further back closer to the widepoint?