I know exactly what you mean about the non-solidness, i think. I have that problem sometimes, but its easily fixed in Lightwave. I dont know much about programs other then Rhinoceros 3d, Lightwave, Maya and Max. If you're thinking about taking on 3d modelling, i recommend either Lightwave or Max, as they're simply the superior programs. Only thing i ever used that was better is Maya, but its hella expensive, and hell of a lot harder then the others. Hmm... Where can i get this model changing program ?