Hi Jim, so a fillet of 0.04 appears to work but not any larger than that. But that's not due to running out of space, the filleter seems to be getting confused about something.

One thing that I've noticed before is that the fillet engine that MoI uses does not seem to like it when you have planes fragmented into multiple smaller plane pieces that are joined together instead of larger simple planes. You've got a few areas like that in this model (co-planar fragments adjacent to one another), so I'll see if replacing those with a more simple larger plane helps any.

- Michael