By adding additional constraints as described in the previous eLog to the model I was able to get a convergent solution using the stationary solver.  I cleared meshes, solutions, and history and uploaded the file in its current form.  Using the stationary solver, we get Umax=1.51646*10^-10 J instead of the 1.52887*10^-10 J obtained using the rigid back constraint.  This is less than a 1% difference, so it is still off from the analytic solution by a factor of ~4.  I will look through the model and analytic calculations again and see if I can find anything which could contribute more than a few percent difference.