the brummel splice is great for a mid line splice.
http://www.neropes.com/SPL_12Strand_EyeSpliceBrummel.aspx


I personally have a 3mm dynema line with 2 end splices. one is luggage tagged around the clew and the other end hasa small eye slice that i run both ends of my spin through. i simply tie a figure 8 in each end as a stopper knot. the eye slice is big enough for the 2 lines, but the stopper knots cant slip out.