Kurt, The length of my drop line is almost always the same around a foot +/- an inch or two. I have caught fish on a drop jig with less than an 8″ drop line. The longer the drop line, the higher off of the bottom your long line begins.
The length of my long line varies depending on conditions and location. Most of the time I fish with 5′ to 6′ long line. This way my long line will wash up on top of the wingdams while your drop jig stays down in the trough at the front base of the dam. Some of the shorter dams will require a shorter long line and some of the taller dams may require longer long lines. I wouldn’t get much longer than the length of the pole you are fishing as you have to be able to reel the fish to the surface.
Eyehunter