We don't have many lfs' here, and the ones we do have aren't big. The only lfs that we have that has bowfronts in store, doesn't have them filled with water. So its hard to imagine what the distortion, if there was any, would look like.
The tank will be my dads and he is a beginner, so hes a long way off wanting DIY stuff, so distortion is the only proplem he is really worried about.