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You could test your spa each season, yes. OR you could go by the C.E.C. standard and test it on a 60degree day, disregard the wind, sun, and contact with the ground . They are all irrelevant in the (C.E.C Cal-poly test).
They may be irrelevant in the test you cite, but they certainly are not in reality.You know what? Skip it. Go ahead. 8-)
Clearly Doc is Einstein. I have no idea what you wrote.