I don't usually use the drip trays with aftermarket rocker assemblies, because they typically have to be cut up to fit. However, if you go without the drip trays, be sure to run restrictors in the oiling passages in the heads. If you don't do that, you will end up with a bunch of oil in the valve covers and not very much in the oil pan. The drip trays work really well at funneling the oil back to the valley area and back to the pan, so if you don't use restrictors, make sure to use the drip trays.