My bad; should have scanned back for the pictures.

Using the Hazen-Williams calculator here, for the pipe between the pump and the filter (3xL; 1x branchT; 8' pipe => 20' equivalent length), I get a head loss of 9ft at 80gpm and 11ft at 90gpm. Using the Hayward chart I sent you, Mark, I calculate the drop through the dumb-head Tee layout as 3.5ft at 80 gpm and 4ft at 90 gpm. Estimating the equivalents lengths of the 1.5" piping to the pool at 50ft, and splitting flows evenly at 40gpm each and 45gpm each, I find a loss of 6 ft at 80gpm and 8ft at 90gpm

Taking filter pressure at 49ft, I estimate TDH around 57.5 ft @ 80 gpm(9+3.5+6=18.5) and 62 ft @ 90 gpm (11+4+8=23).

also used Charlotte Plastics Design manual