Looks like a pretty good first try. A couple of suggestions though. The eyes may make this ride upside down for what you have it tied. Actually with a crawfish riding point up works better because you can imitate a real one better. I tie mine to ride point up. I let it fall to the bottom, watch it closely as it does because they hit it on the way down sometimes. Then twitch it a few times and let it drop again, repeat.
Also you may want to lighten up on the claws a bit and if you do a couple wraps around the bases, you can get a pretty good spread and shape. I use Squirrel tail because it works good and they keep committing suicide in the roads I drive.
Also on the carapace, if you get a good shape you should make a pattern so you don't need to guess each time you make one. I use thin skin and it comes on a paper back so when you get a real good one keep the paper. Instant pattern.
Pretty good looking fly though. I'm sure it would catch fish.