Found a specific paper that talks about sub 10 nm pores done with an Helium FIB. So, it seems that Storms requirement for gap size is achievable.
Looking at the feasibility of creating a thin film of Pd with sub 10 nm pores, I wonder if a thin film disk of 20 mm diameter and 0,1 millimeter thickness as used by Liu et al as reported in this paper:
could be used to repeat the experiment with the nano machined sub 10 nm pores produced in the Pd. These experiments were done with solid Pd disks and still were successfull and showed energy densities that were indicative of nuclear power, and probably lend themselves to be performed within the constraints of Seebeck calorimetry, specially the version of this that is done with Deuterium on one side of the Pd thin film and vacuum on the other side, which stimulates the flux through the thin film, as reported here:
Don't know if anyone agrees this would be a straight forward experiment to test the nanomachined gaps, or not.