Jay's right about the egg patterns sinking when they get wet. They go down, but typically without weight, won't sink to the bottom. I don't weight the pattern itself. I do tie my eggs on a 2x heavy hook. That does help in getting them down. To make sure they are on the bottom I'll attach splitshot to the tippet, making adjustment to the number and location along the line according to the water conditions.
Here's one of my favorite patterns. McFly Foam in you're choice of colors, a bit of crytal flash for the tail, and a wisp of synthetic pillow stuffing for the veil. Been a deadly fly on the Lake Erie Tribs when the Steelhead are taking eggs.