Good idea, it's always best to try things for yourself.
I recall Gordon Strong saying that while phosphoric acid is neutral but using more of it in high alkalinity water leads to a soda pop type flavor. I agree. I think acid is best used with water under 100ppm ALK or so. If that were my water, I'd cut 50/50 with RO for ales and do 100% RO on lagers. I fooled with lime treatment but felt it was too time consuming. Really cool to see the science though...
I'm probably misunderstanding or oversimplifying something regarding the pH of aqueous solutions or whatever, however I do also feel compelled to share a thought with you all, which you can feel free to research and validate or refute....
A very long time ago, I think I learned in college a general "rule of thumb": that nearly all phosphates (except hydrogen phosphate, a.k.a. phosphoric acid) are insoluble in water. As such, I have always figured that this is likely why phosphoric acid is so flavor neutral, because anything it touches, at least in water/aqueous solutions, turns into some insoluble solid mass
that precipitates out of solution, which unless you eat it on purpose, you should not taste at all in your final beer, because it cannot
be in the beer!
So, if you can taste a "soda pop" character from too much phosphoric, then you've likely succeeded in completely obliterating any and all cations that may be dissolved in the water, leaving behind nothing but H3O+ hydronium (a.k.a., H+) with the phosphate (PO4---) and maybe some other anions, which is I think is very unlikely unless you were to use just a ton of it.
Martin or others, feel free to fix me where I'm wrong.
EDIT: Looks like sodium and potassium also play nice with phosphate, as well as ammonium. Not that it matters much for most beers besides like gose or something like that.