Hi Everyone - I see this topic covered often, but it always has to do with creating a hollow object from scratch. What I'm having trouble with is in making an existing object successfully hollow (and for printing, not just for computer viewing). Here's what I'm trying to do...I downloaded a model of a human head from Thingiverse. I'm trying to take off the back half of the head and place an object inside where the brain would be (it's an art thing). Taking off the back half of the head is easy with programs like Meshmixer and the like. But when I go to prep it for printing, it just won't work. I get warnings about things like holes in the mesh or split manifolds, but when I try to auto repair those the head inevitably gets filled in solid and I'm back to square one. I'm sure there must be an easy way to accomplish what I'm trying to do if someone could just get me started in the right direction. Any advice?