Those heads are designed to be used with a technique called "flick shaking", which is a finesse bass technique. Kind of like wacky rigging but with a little weight added. Hook your worm in the center with both ends hanging. Anyway, jigheads with that type eye bend (30, 45, 60 degrees) tend to be used a lot with swimming retrieves for bass, and should provide the same benefits for crappie, though you don't see them utilized much. Should be good for trolling, though you'll have to watch for rolling of the bait, as the straighter the line tie and more centered the lead weight (less keel effect), the more likely the bait is to roll, especially with bulky baits, lighter jighead weight, or faster trolling speeds.
-T9