I usually figure 2/3's of the amount of line behind the board will be the approximate running depth, but speed does affect the depth a bit. So you want to run the jig(s) 6 foot deep, put approximately 9 feet of line behind the boards I've never use 1/8's on boards, usually 1/32 or 1/16 but if that's what the fish want, that's what they want.