Ok, just started my renovations in earnest on my 71 Oday 23 poptop, took the first cut on the poptop to replace the core and it was gone. Noe I need to pick ya'lls brain and see if anyone knows what type material this was. The wood was so rotted, it disintegrated on me. As this is the top, would 1/2" marine plywood be better or do I need to go with balsa to keep the weight down. I also looked at the foam prefabricated material. About the only stress I have will be on the halyards I want to reinstall "correctly" this time for single handing which consists of a cam and a pully at the bottom of the mast. Would a combination of both, using perhaps foam and then wood at the stress points be feasible? Just asking here and trying to get ideas. My gut tells me to to go with the plywood for a longer lasting product.