Hello... I've been running into some problems with a model I'm trying to prepare... in Blender. It's a low poly model that has subsurf applied but before I upload to print I Alt+C to convert the modifiers leaving me with a high-poly model. While it's in low-poly mode it's easy to handle and I can see what's going on... when it's in high-poly mode there's verts all over the place and I find it difficult to see what's going on. My model is being returned with a "Only manifold objects can be printed" problem and I'm trying to find the problems using Select > Non-manifold and I can't see anything. However, in low-poly mode there are no 'doubles' but once converted there are several hundred. I assume I have to convert the modifiers first but to what level?! My guess is I'm going too high. My model is about 80,000 polys. Any other ideas greatly appreciated.