I'm in a hurry but here is a link to my photobucket.
http://s190.photobucket.com/albums/z...nids/?start=20
It contains images of a Carnifex I converted into a scorpion, it may give you a few ideas. I left a post in the rules section for you. I think that the twin tail is interesting and you should consider that at the moment it is the only distinctive feature you have described concerning this thing. Basically it is a Carnifex with crushing claws and two tails. If you ditch the twin tails you will be left with a Carnifex that has only crushing claws which is one less weapon than normal, basically a small Carnifex.
Get some more ideas about what this thing looks like, details etc. If you want giant claws try these.
http://www.forgeworld.co.uk/acatalog...RANIDS_13.html
The two stone crusher claws could certainly give it a nasty look, they count as crushing claws and rending claws in the game.