Went through a similar episode back in 1982 with Dad's 1975 18'SS. Rib Cracks, not the Corrosion. Dad spent big cash having it repaired, reriverted and Braced, only to have it leak again in a few months.
I think the V5 Hulls had the Rib Cracking remedied, and my Uncles older 1964 Holiday never...