you want it so the fishfinder doesnt go down to the hook as this will usually knock your bait of the hook . I do pictures so here is the way I do it . running line 20# ,fishfinder rig ,swivel ,50# leader ,hook either with a snap or snelled . This keeps your fishfinder with the appropriate size sinker from riding down your line to the hook . unless you tie a big knot

. a bead after the fishfinder that wont go over your knot might work , my problem with that is the constant smashing into the knot may cause it to weaken and yes it does the same to the knot at the swivel . I have never had a problem rigged like that .