Importing models for editing?

[Hingemadness]

I have a very simple cylinder that i would like a modeler to add details to upon the surface (musculature). I plan on exporting the SW parts file , have them work on it in Rhino 3D for example and then import the part back into SW and add some precisely measured features.

THus far i have not had any luck. Has anyone been successful with this technique ? What am i doing incorrectly?