Ralph, It's been a long time since I have looked at a psi chart. My bad as I should have prior to making my earlier comment. From the 3 charts I just looked at you are correct in that the 03 nozzle is the correct one. For my 5.5 gpm @ 3500 psi set up all the charts also say the 03 nozzle is the correct one which the 1503 is the ones I use more than any (with the 2503 used for lighter duty).
I will add, however, I sometimes use the 1502.5 or 2502.5 nozzle when I am far away from my machine running through 100's of feet of hose and my psi at the surface cleaner drops to closer to 3,000 psi or less (with the 03 nozzles). I am already losing some flow by going through so many feet of hose dropping my psi. By changing to the slightly smaller nozzles (02.5), my psi will kick back up closer to 3,500 psi at the surface cleaner (per my gauges at the pump and surface cleaner) to allow me to clean better without any noticeable additional water loss in bypass.