Hi @rwilcken, Firstly, as long as this is the desired shape I don’t think I see anything wrong with it. It is water tight. I think you simply need to increase the number of cells in each direction, consider tripling it to start. I would expect this to give better results and increase the cell count or refine locally to improve it.
Finally, I use OnShape, you may have heard of it but it is very powerful and also free to individual non-professional users ideal if you just need to put a geometry together for SimScale.
Let me know if this helped or you need any more help,