Another tip is to think about what you will do when bringing the downrigger up...especially if the bottom line has a strike. Manual downriggers are no problem, just watch for the clip, but with electrics its really nice to have a stop set for the top clip. I use electric scottys and add an extra stop on the cable for the top clip when fishing multiple lines. This way the downrigger will automatically shut off when the first clip comes up even if you're not paying attention cause the fish is fighting hard. I fish them as close as ten feet vertical but you have to be careful when dropping the gear or turning.
Hope this helps.