I was in the process of mounting my new grand slam outrigger bases on my 1995 balsa core hardtop. Outside side shell of hardtop was in good condition but the balsa core had deterioration due to water intrusion where old holes were drilled and not properly sealed (previous owner) after cutting out the holes for bases I used a screw driver to reach in the void and loosen the rot (now dry) and vacuumed the dust and particles out with a shop vac. I then filled the void with low expansion foam. Good as new! Mind you this hard top is not one that you walk on even in it's original state, so I wouldn't recommend this fix on a load bearing surface.
