An old fishing adage states that you shouldn't mix lures and bait in your trolling spread. There's some merit to that, as you can't troll as fast with bait as you can with lures lest you tear the baits apart. But dragging lure and bait together is what I attribute (besides experience, dedication and yes, luck) to my win in the Mahi division during the 2008 Hampton's Offshore Invitational.
My method is two-pronged. Rigged ballyhoo swim like a lure and because of their streamlined shape, can be trolled faster than live bait or split-tailed mullet without spinning, breaking apart, or otherwise becoming unattractive to the fish. So I drag ballys for that reason, and because, pretty much every bluewater species eats them like candy.
The second prong is particular to those times when gamefish hold deep, rather than swimming at the surface and pushing water. When the fish are "down," I'm a firm believer in getting their attention in a big way. This is especially true with a small boat like my 23 Regulator aboard which one can't troll a nine rod spread due to narrow beam and other factors. That's why I always have some Stalker Spreader Bars or honkin' big pushers in the 20" range to drag with the ballys. Spreader bars and pushing lures make a lot of commotion and, while they can be trolled at relatively high-speeds, say up to 7 or 8 knots, they still create a fish-attracting ruckus at the 3-4 knot speed that I like to troll my naked (unskirted) ballyhoo.
My spread consists of a spreader bar and pusher on each of the two flat lines, clipped tight to the transom and close-say two waves back in the wake. The distance is nominal depending on sea conditions, and I may drop them back or reign them in a bit in order to get just the right enticing swimming action I'm looking for. I drag ballyhoo on the left and right long positions, about 6 waves (100-feet) back, and shotgun another naked bally real deep, say 9 waves or about 150 feet back. This usually brings 'em up from the depths and proved successful for me during the 2008 HOI tourney. I nailed a yellowfin tuna, a white marlin and a total of 18 Mahi. Not the most spectacular catch, but there were many larger boats competing, with paid crew, who came back fishless. So relative to the action during the tournament, I did well.
Old adages like "don't mix lures and bait" are often worth heeding. Just don't forget my favorite old adage: There are no rules.