If you are fishing deep, jig size doesn't matter. You are going to have a weight on the line holding it vertical. You also want your speed to stay slow, don't move so fast that your bait will be above where the fish are holding.

When the crappie move shallow I will use a 1/32 or 1/16 jig head and use a float. I like the jig to be 3 to 5' deep. I don't use added weight, you want the jig to move freely. As you more your boat around the jig will rise and fall. Most the time the crappie will hit the jig on the fall and this is where the 1/32 come in. If I am using minnows I will use the 1/16 jig head because of the bigger hook. The 1/32 head comes with a #4 or #6 and you can find the 1/16 head with a #2 hook.
The main thing to remember is (keep it slow) when you think you are moving slow enough slow down a little more!!!!
Good luck, spider rigging is a great way to catch big crappie.