Duct Tape (Score 2, Funny)

If and when those cracks propagate to the surface, with a crack connecting a void to the surface, then you have a mechanism for cryopumping. When the tank is cold, air is ingested. It liquefies and goes into the voids. Then as the tank empties and the [air] warms up and evaporates, the resulting pressure blows the foam off.

How about this idea... DUCT TAPE! It might also solve that so-called heat tile problem...