pH levels -- they won't stay down

[waterbear]

Until the plaster is fully cured (and that could take as long as a year) you are going to have a very high acid demand. As the plaster cures it will leach out alkaline material into the water. It is the nature of the beast, unfortunately. Keep up with the testing and the additions of acid as needed and do not let the pH spike high if you can avoid it. This will insure proper curing of the plaster with minimal chance of scale formation.
(THIS is one of the main reasons I chose fiberglass for my own pool!)

[Watermom]

Do NOT buy dual action trichlor tabs. They have copper in them and you do NOT want copper in your pool!!! Just plain trichlor tabs.