The TA of your fill water has nothing to do with whether a Bicarb Start-up is good to do. An acid start-up or a pH neutral start-up both maintain negative CSI during start-up and the traditional start-up maintains a near zero CSI and all three create plaster dust to varying degrees which means that the calcium carbonate in plaster is dissolving into the pool. With a bicarb start-up the calcium hydroxide produced from curing is converted to calcium carbonate IN-PLACE in the plaster forming a sealed plaster surface without generating plaster dust. It results in a smooth hard plaster surface that should be stronger and last longer.