Under what conditions would viruses assemble like this naturally? And can colloidal membranes be formed with rod-like molecules rather than viruses?

Could you discuss the positivity vs negativity of kappa bar a bit more?

If kappa bar is positive, and topology is not fixed, then wouldn't the system be unstable to the formation of holes? Since the total integral in the 2nd term in your energy is proportional to the Euler characteristic which becomes more negative with the addition of a hole?

Yes, I think you are correct Greg, but the line tension might suppress holes..

it does seem to give a lot of holes!

Euler buckling generally talks about a critical force needed for buckling. Do you have any such relation and if yes, on what parameters does the critical force depend on?