The final solution was using a 1/2 inch cap with a 3/8 inch hole drilled dead center. Keywords DEAD CENTER, a little off center and you no longer have a vertical water plume. In this case, the type of pump did not matter. This was a 700 gph mag drive. The 3/8" hole increased the height of the water plume four-fold, which was too high. This was easily corrected by reducing the flow rate.
I would still like to know the formula for determining the effect of flow restriction on PSI. I know there is a formula, engineers have one for everything.
"Everybody is ignorant, only on different subjects." - Will Rogers