Well Fay I'm a bit dubious about this, as you know. ( And so is my buddy Layton )
However, fingers crossed, very much hoping this works out for you.
You must keep us posted. Maybe at higher Po4 levels it will be OK, but when they come down you will have to be careful.
By the way, that brown algae you mentioned the other day, it may have been a brown slimeyish film you get from overdosing start. If so, the film is actually bacteria, and not a bad thing for water quality, just looks bad.