Since you have a vinyl pool, you can't have corrosion in the "calcium carbonate" sense which is why you don't have your CH up at 300 or so as you would in a plaster/gunite pool. Corrosion of metal surfaces (especially stainless steel, galvanized metal, and copper) is unlikely to occur if you keep your pH above 7.0 at all times and I would just shoot for around 7.4-7.6 which is generally better on the eyes anyway. The purpose of TA in your vinyl pool isn't so much to prevent corrosion as it is to act as a pH buffer, but you don't need much of it to get this buffering effect and as you've found out, too much is not good either as it causes more CO2 outgassing (and pH rise).

Richard