Usermat: Linear viscoelastic model with geometric nonlinearity

Hello,

I have implemented a linear viscoelastic model using the user subroutine Usermat in Ansys.
I have used the classical paper: "Formulation and implementation of three-dimensional viscoelasticity at small and finite strains" of Kaliske & Rothert (Simo's approach) and it works fine for small deformations.

It is written in the documentation that in the case of a simulation with large strain (geometric nonlinearity), one must rotate the state variables.

I would like to simulate bending of layers (like a shell, but made of solid elements with only displacement as dof). 
Do I have to rotate the state variables because of possible large bending (rigid body motion) even if the local deformation (strain) is small (I activate the option "nonlinear geometric" in Ansys) or can I update the state variables as in the paper without rotation at the end of each time step?

If so, how should I do that. At the end of each time step, I just multiply the tensor of state variables with the rotation matrix and save then for the next time step? Do I have to rotate any other tensor or the old state variables at the beginning of the new time step?

many thanks

Xuxa