Student needs help with FilletEdge!

I need to make a Mr. Potato head for school, and I am making the arm and hand at the moment. I made an outline of the hand, and I extruded it. To make it look more realistic I tried the FilletEdge command with a radius of .3 but it failed. How do I do a successful FilletEdge?

Mr. Potato Head.3dm (7.3 MB)

Using only Rhino tools, I’d approach the hand something more like this attached file. Sweeping an arc between two rails and a mirror, rather than an extrude and trying to fillet, after the fact.

HandApproach.3dm (763.4 KB)