Even if the backing blocks were minimal (say, for instance 4x6" of 1/2" aluminum plate) that would have to rip out a substantial portion of the surrounding deck. That would take tons of pull (one would assume). I can't imagine anyone building a boat without any backing blocks on the bow cleats. Could it be they only used washers? Or maybe the tow boat was just too aggressive on the throttle, with too short a tow line?