Hello, I am very new to modelling and 3D printing, but I was hoping I could create something pretty small and simple. I used SketchUp to create the model, very basic, and I uploaded it and the pricing is fine for me. My concern is that it's going to be hollow. I actually have no idea how thick the plastic is going to be. Is there an easy way to "fill it in"? I'd like it as solid and non-squishy as possible. Any other comments would be appreciated. Attached the file.