TA is your waters ability to resist PH change. TA is important to PREVENT wild PH swings.
Here's a question - If you have a PH of 8.0 and a TA of 50 (I don't know if this could happen), Are you saying you need to get the TA up in order to keep the PH from swinging?
If you were to use Alk up it would raise the PH too (at least in my limited experience), you would then use PH down. But your adusting the Alk as you do this. This is why my statement of "It is my opinion that TA is not too important as long as your PH doesn't swing wildly" ... If a water's PH doesn't swing wildly at a low TA why adjust the TA as it effects the PH.
Quite honestly, my tub reacts to baking soda differently than my pool. As I said the baking soda raises both the PH and alk together but in my pool I need to add a PH increaser as my alk reaches it's level before the PH.