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Unless you refurb them yourself....I would stay away from someone else's problems
A used full foam hot tub with freeze damage? (Are these full foamed?)No. Who knows what else was stressed, the extent of the damage. I wouldn't. These folks may end up paying someone to haul it away. Offer to take it away for free.
Not full foamed. They call it their Arctic foam packsge - 5" or so on the inside of the shell.