I am a new to sailing. Having just purchased a 1979 O'Day Widgeon, I am looking to make it solidly "turtle" proof. She's go the foam flotation in the hull but I would hate to have her invert all the way. How does one calculate the floatation requirements for a Masthead devise.? There are foam and inflation types that are "precious" on the pocket book. Does one base it on the weight of the vessel? Should I bother with pursuing this safety measure? Thank you to one and all.