[flyingfrizzle]

My 71 had the quad stringers. They didn't have foam in them but did have foam between them in the voids. The earlier 4 stringer grid stringers are far stronger than most boats and with no wood there is no rot. Only worries are if there are any cracks along the 90 degree areas where they have flexed. The only ones I seen damaged were from extreme beatings and that was on the large box stringers not the quads. If you find wet foam anywhere, get it gone look for stressed areas (you will more than likely not find any) and worry about the deck balsa and the fir in the transom if original. That is the only areas that normally have issues. Some hulls have rotted wood in the caps if lots of holes were drilled in them but the older 69-72's had super thick cap layups so may be ok there. The awesome stringer set up in these hulls are what makes them so good for rebuilds, I is one thing less to redo.