Welcome to our forum.
Nice post, long time buddy, you need to check in a bit more often!
You were in New England area right Stew? Sorry we forget those less traveled here. But you've always been a respected member here. Screw them others.....
Chlorine in spas needs to be stablized becuase of the hot water and volitile environment which is why I always suggest customers to get their products from a local dealer who not only carries stablized chlorine but can explain the danger of tri-chlors and cal-hypos that arent stablized. The sodium chloride being produced from salt generators would also be considered "Unstablized" and could use some CA.Cal-hypo is one of the products that I see the most damage from in the field when used in spas.
Not a single use but over a very short period it attacks the seals, dicolors and peels pillows, leaves a white film above the waterline and clouds the control screens. My guess is that most have used it for at least a month by that time.