That little mesh is quite untratable.
Well, in the mean time you can just make what I do, and actually some people do in games when the authoring geometry.
Decimate the mesh to the point that is manageable.
Them, attach it as a child node of the visual mesh with a hidden attribute and an indentity transform as offset matrix.
The in your plugging you can search for the child nodes that has attribute collision, and use that to build the collision shape.
If you load any of the fbx vehicles, or other models in the sdk, you will see those meshes that I place as colliders.
I also add dummy nodes as hard points for attaching joints, or getting a frame of reference. Basically use the hierarchy for authong the mesh and leave the graphic to do what it does.
Artist and designers love that stuff, it gives them a sence of ownership when using the tool.
Also you will be surprised at how good are artist at hand authoring those models.