I am new to spider rigging, but I can only catch crappie over brush piles 12'-18' of water, what I started doing is buying the small plastic/rubber bobber stops but keep them up by the reels, that way when I finally find the fish and what depth I think I can catch them at I will set all rods at same depth, and if I see something that makes me want to change depth I can move the rigs and stops. That has been working for me on the last couple trips.
Aaron