I fairly frequently run into problems with boolean unions not deleting the internal geometry. I often resort to going through and cleaning it up by hand, but I feel like there should be a better way, and this one would be a bit taxing to do manually. Both structures are solid, fully manifold objects, they don't share any faces, and I have recalculated the normals on both of them. I took a picture with it lifted up out of the object because its too much of a mess in wireframe mode, but when I do the boolean modifier you can clearly see the point of the support still exists inside the object below, and I would have to go through and clean them up all the way around the circle. Any tips would be appreciated.