Thank you for the clarification. If the Static optimization (SO) tool ignores the passive force component, is the force that is computed incorrect? I assume that this is a valid approximation, but I can't find the justification anyplace. If the "a" resulting from SO is applied to fm=a*fiso(fl*fv+pfl...

Were you able to solve this problem? I just downloaded the model, and would also like to be able to see the ribs.