When using Sandshrimp, throw a HALFHITCH AROUND THE END OF THE TAIL TO KEEP IT FROM BALLING UP ON THE HOOK. If your using prawns I'd use the whole critter. I've been using this rig for both trolling and anchoring and caught fish.
I tie two 3/0 Gamis moochinig style spaced about an inch apart. Above that I put on a sliding clevis with a spinner wire cut off at about 2.5" to straighten out the prawns tail. Above that two rainbow corkies and a thin fin or whatever they are. Insert the second upper hook at the bend in the tail of the prawn and let the front hook just hang. Straighten out the prawn and insert the spinner wire to keep it that way.
I think that if you have good prawns, they are way more durable than sandshrimp. You may already know all of this so take it for what it's worth. Also I hit my capslock in the beginning of this post. I wasn't yelling at you, just too lazy to go re-type. Have fun and good luck!