Model from maya deforming incorrectly

Seriously bashing my head against a wall with this one. For some reason my model is deforeming strangely in unity... I've tried different unity versions, checked normals (poly and vertex), im only using 3 bones in maya and have the correct interpolation settings to ensure its not using more.

I've tried FBX as both binary and ascii and a bunch of different maya export and unity import settings (strangely bone settings in unity dont seem to make _any_ difference to how the mesh deforms).

The attached images show the deformations in unity and maya, and a wireframe of the unity deformations.

If anyone can provide advice i'd really appreciate it... I honestly hope it's something that i've done wrong in import or export so I can fix it and be consistent in future... but I haven't had this issue on the other couple of models i've made. I even rebuilt the entire mesh to ensure it wasn't a topology issue so i'm sure it's something odd in the bones, or the skin conversion.

 

Are you running the highest quality mode? for me it looks like low quality, where bone bindings get simplified. Project settings->quality.