Taylor Watergram Balancing Calculator Question

[PinkFloydEffect]

I am working on balancing my hot tub and I am under the understanding that a saturation index of -0.3 to 0.5 is considered balanced. So I started playing with my calculator wheel using my perimeters. I keep my calcium hardness at 80ppm and my alkalinity low at 80ppm as well. My level of CYA is kept at 30, and my temperature range is 100F-104F. If I understand the SI correctly a rating of 0 is best balanced? Plugging in the data I just provided above, to have a balanced water rating of 0 the perfect pH would have to be 7.9 instead of the 7.4 target the tub manual says. Is this okay or should I double my calcium to 160ppm in order to have a lower pH of 7.4? My tub already likes to run 7.8-8.0 so is fighting it worth it just to have harder water?? 

[Smorgasbord]

They say that the ideal range for ph is 7.4-7.6. For calcium hardness it's 150-250 for a hot tub. The way I understand it, the watergram is useful to balance things further after they are within those ranges. So yes, 0 is the best balance, but if you raise your CH to 150 you could lower your ph to the 7.4-7.6 and keep the water balanced.

Now, from what I understood, if the calcium hardness is low your water will have a tendency of dissolving concrete, plaster etc. Depending on the making of your hot tub, this could lead to damage over a long time, so that's the main reason you might want to increase it.

All this I've learned from reading the little Taylor booklet, so take it with a grain of salt.