So, I'm figuring that I added the DE to quick. The bonus is that pump pressure rose back to 15 psi which is 1 1/2 psi higher than when I started. I suppose that as the pump ran and circulated the water the DE was re-collected in the sand filter and the pressure rose back up. I vacuumed up what settled to the bottom of the pool and I'm going to assume that it is now sitting on top of the sand as well. I'll check tomorrow to see if anymore has settled to the bottom. If not, then I figure everything is good-to-go. If four cups is to much, then I look forward to experimenting to see exactly how much gives me a 1 psi jump in pressure. Next time I'll add it slower.