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50 and 60 amp are commonly run with 6 gage wire. Cant you just change out the breaker(s) to 60amp and change the connections at the tub 60 amp (if it's even required on your specific model).My setup has a 60amp breaker on the main panel running to a spa sub-panel with 60amp GFCI breaker.That's about $90 in parts (if memory serves) and less than half an hour of labor.So I think you need a second opinion on how to upgrade the service. I'm skeptical running new wire would be required.
Whatever tub we get will be going in the corner of a roof deck.
Ok, we just christened our cameo last night.....we were outside in 29 degrees in the snow temp had been set at 101 and had dropped slightly to 99 in an hour. That was with the heater still running. Good luck on your search!!!!!!!