Hollowing in Meshmixer

Hi all,

I want to hollow out the inside of my model and have been using Meshmixer to try and do this. However after I enter all the hollowing settings and hitting accept, if I do a cut on the model so I can view the inside, I am seeing red (literally). Apparently STL files can have outside faces and inside faces, and Meshmixer is making the hollow an inside face. The problem with this is that the model is no longer a closed 'solid' STL. If I open it in Netfab the faces are red, even after I do a repair. And the slicing software I use doesn't recognise these 'inside' faces and the model becomes buggy (I actually don't know where this method would ever be useful).

Does anyone know how I can hollow a model in Meshmixer without the whole inside/outside face thing. I just want a normal STL file that I can slice properly.

http://i.imgur.com/wvuIgmt.png