What is the best way to rig, say, a 3 inch power craw on a bass jig??

I normally rig mine so that the trailor is all the way up to the jig head when using craw immitator. If I am using a chunk I just hook through the fat flap in the middle and let it swing.

Craws flee backwards so make sure the pinchers are behind the jig.

I exclusively use the Strike King Pro Model jigs.  I am not sure if anyone else uses the feature that comes with this, but I feel that they have a "trailer" keeper system between the rattle and the shank of the hook.

I will insert the hook point of the jig's hook about 1/2" into the trailer, and then, I would push the trailer up between the rattle and the hook shank, and it will hold the trailer in place.  After about 12-15 bass, I have had to change the trailer.

There are a a couple things that I do with the plastic trailers, which are the Zoom Super Chuncks.  Sometimes, on the very ends of the legs of the trailer, there are imperfections in the pouring process that will leave small additions.  I trim those off, and then, I will cut up the middle of the leg, about 1 in., so that it will look more like the pincers of a crawfish.