If you are planning on structure trolling, often we just run all lead on the reel (with a leader of course to connect to the lure). To get spread we use long rods in rod holders.
If you are going to be fishing suspended fish – and know the depth you need to get to – then we splice in the lead core (backing of mono, leadcore, leader). This allows you to let out the leader and lead then attach a board to the mono backing. The boards will run better not connecting lead right to it.
Now, the exception to this is when I go to a new area and don’t know how much lead I will need to get to the depths the fish are biting at. In this case I use all lead on the reel and actually hook up lead core line to the board to try to figure out how much is needed. You will need a good board like the Off Shore Tackle Side Planers to stay upright with leadcore directly attached. Once you figure out how much leadcore is needed – then you can rig up spliced set ups.