The shape at the bottom is to make the waves end points level. If I make the bottom surface of the wave flat, the end points of the wave stick up in the air, it took me a lot of trial and error to arrive at this and for me it works much better than a flat bottom. Plus it makes the wave look more realistic. There are some others in my gallery. I'm not familiar with Vue lattice tool, so I can't really give any tips on using it, but I do have to plip the wave in Bryce on occasion to get the profile of the wave clean.