Is there a best way to analyze a relatively thin solid body as a shell?

My geometry is modeled as a solid.  Inside the simulation study, I can right-click the solid body and select "Define Shell by Selected Faces..."  This seems to convert the solid into a shell for analysis purposes, at least it meshes as a shell, but here's the rub:  I can't seem to select the shell edges/faces to apply the fixtures/loads.  The faces of the solid are selected instead, and then the solver cannot find the fixtures/loads for the shell and fails.

One work around I've stumbled on is to insert a "Mid Surface" feature for the shell and then a "Delete Body" feature to camouflage the solid for the analysis.  (Applying "Exclude from Analysis" to the solid body does not seem to do the job.)  Then I can select edges of the shell, but it seems a rather cumbersome approach:

Thanks for any recommendations. -- John WIllett

P.S. -- A "Circular Symmetry" fixture, as appropriate for this "pie slice" of a full disk, does not seem compatible with a shell.  (I found I had to apply "Rotation" = 0 fixtures around the two radial edges to simulate this.)  Is this true, or am I missing some trick? -- J.W.