Weight body force in fenics-shells formulation

Dear community.
I have adapted the example found on

https://fenics-shells.readthedocs.io/en/latest/demo/nonlinear-naghdi-cylindrical/demo_nonlinear-naghdi-cylindrical.py.html

For a thin structure subjected to its own weight, with similar boundary conditions.
This is done by adding the following term to the Pi_PSRI expression:

#my modification here : defining gravity vector
gravity = Constant( (0.0,0.0,-Weight) ) # in the downward z direction
gravity_term = inner( gravity, u_ )*dx  #body force, u_ is the displacement field
#my modification stops

Pi_PSRI =  psi_b*sqrt(j0)*dx + ..... - gravity_term  #the last term is mine.

The solution behaves nicely, however this is a 2D shell formulation. If I have a material of density p, how do I correctly implement the body weight in the Lagrangian ? Is it as simple as

gravity = Constant (0.0, 0.0, -p*t )

such that the gravity term has a t*dx term that scales correctly ?

I did not provide a MWE as this is more of a coneptual question than a help with the code.

Any input appreciated

because you are shells, t*dx is the volume