Hi Scott, part of the problem is that filleting doesn't like things that are coplanar to be in separate fragmented pieces rather than one big plane. It's this area here:




With that top replaced with just one single big plane as in the attached 3DM file, that should help it to fillet better. That seems to fillet at radius 1 or 1.5 ok, but not much larger than that, not sure why that is.

- Michael