Very nicely done.
I wouldn't go any larger on the bead. While there are certain flies I like tied extremely heavy, generally my preferance with nymphs is to use split shot to get 'em right on the bottom. I do have a very heavy stonefly I like but when you start making nymphs extremely heavy, you run a greater risk of losing them on snags. You might try a small dumbell eye rather than bead. This will cause the the fly to drift in a hook upward position but still get right on the bottom.