I think you are right on about the action and colors. We have tons of shad in our lakes but most of the time a silver or gray is not the color the crappie want. In Feb. a 2.5'' grub was good and then after the spawn a baby shad would out fish the grub for close to three weeks. Now a 1.5 grub works good.
The bigger baits doesn't scare crappie either. Cranks 3.5'' are working now but only if you find the right color the fish want or you can fish all day without a bite.;)

