sorry but your information is incorrect...Calcium kept around 150ppm is ideal in my opinion, and some systems such as Saltwater chlorine generators like it around 50-100ppm. If you run your spa at 400ppm calcium your are going to run into some issues: calcium flaking in the water, buildup in your pumps, ozone injectors, check valves, etc. and it can even begin to attach to the shell (I've seen it so bad where an acid wash was necessary to remove it)
I'm not familiar with copper systems, but keep in mind there is only a few sanitation methods that are EPA approved: Chlorine, Bromine, Biguanide, and silver ion/mps....A copper based system is NOT epa approved to use in a hottub as a standalone product just so you know