Hi Leonard, it is looking really great so far!

re: Failed fillet - it looks like the object has a pretty small thickness in that area.

That will limit the fillet radius or chamfer distance to need to be a really pretty small value in order to fit within that small area, like maybe something around the range of 0.01 or so?

If you can post the .3dm model file here, or send it to me at moi@moi3d.com (if you wish to keep it private), I can take a closer look at it.

- Michael