Sounds like you are making things awfully complicated. I usually don't fish double rigs but when I do I use a loop knot like Mitch was telling you. Now if you want to pre-rig doubles, get you some 8lb fluorocarbon and tie a jig on each end. Use a couple of feet of the fluro. Tie a loop knot in fluro leaving more line on one side of the loop and shorter end on the other. Loop tied in fluro won't slip. This is how I prerig doubles to speckled trout fish except I use 20lb fluro