Yeah a 5-6 foot piece of 8-10 lb should do perfectly fine. If it is just the tippet section not turning over, then give a foot or two strip back, and bam, level line. Not super important in this situation since you will also need to allow the fly to sink a little bit as well, so that can take some slack out of the line. Another thing I thought of, you can, if you choose, to change your cast as well. It isnt efficient or anything, but I managed to toss a heavy marabou streamer with dumbbell eyes, size 6, on a 5wt, with a 9 foot 4X leader. It was hell to cast, but it caught fish! It was a completely different cast than an unweighted nymph, the timing was off and the plane of the rod never traveled in a straight like, to keep the fly from hitting the rod, but if you power through it, you can manage that, it does end up turning over. And it should be easier if you are fishing an 8 or 9 weight for salmon, with a heavier leader, tapered or not. Just takes a little practice. Or sometimes a lot. Depending on how good youre feeling that day!
Come to think of it, this video was when I was using that same type of fly. You can see the wide open loop on the forward cast, and the way i bring the rod around on the back cast.
http://www.youtube.com/watch?v=s0pc6Vgc-04 the fly in question