Problem with radius of gyration is as follows :

Lets take your Boat A = the stock Marstrom Tornado built of S-glass and aluminum spars.

Keep your boat B is a tornado made out of imaginary stuff that is infinately strong and stiff so it dosen't weigh anything. This one has a reduced radius of gyration and performs better.

Then we introduce boat C this one is the same as boat B but has a given weight strapped to it dolphin striker pin. As the radius of gyration is defined as "Moment enertia / totall mass" we can say that this boat has a reduced radius of gyration as well ! But we all know this boat to be a worse performer. So the net result is one where the radius of gyration is reduced and the boat performs worse.

In the imginairy case we could strap an very large weight (infinite even) to the pin and arrive at the same radius of gyration as boat B. Naturrally this boat C will have far war performance than boat B because it will be on the bottom of the lake ar form a black hole (different topic)

Point of this example is that a similar reduction in radius of gyration can be had by both increasing and decreasing weight; both leading to better performing and worse performing boats. Radius of Gyration, although technical useable, is therefor a traiterius principle to use.

Moment of enertia calculations don't have this problem and will assign a higher value to boat C no matter what the added weight.

Wouter