PVC? Wouldn't that move too much, too much flex in it?
When we used to use pipes we used 1" EMT Conduit, it worked pretty well. We would get an 8' or 10' 2x4, spread the pipes about 7'8" or 9'8" apart and screed, in wide open areas.
Now we only use string lines and a board, no pipes. Much faster, better end result, no worries about tamping around pipes and so on. We set all the string lines with a laser, then mark the 2x4 at the elevation of the brick and screed along a string line to keep the same plane.
Takes a lot of practice to get good at this technique, but it's worth it.