I'm not sure who your are direction your comments to...
Placing electronic devices in a metal box is just plain silly unless one knows the freq and harmonics of the EMP. You would have to build a freq dependent Faraday Cage;
-A nuclear EMP/HEMP is essentially "DC to daylight". No special frequency calcualtions needed.
A Faraday Cage (a box with holes in it) is an approximation of a sealed metal box. If you don't try to save money by using an approximation of a sealed box, you don't need to worry about frequency holidays or response.
both impractical and cost prohibitive.
Certainly a bother, and not useful for operating equipment. But again, for a few pieces of equipment, it is easily and cheaply possible to put them in a sealed box.
Grounding and disconnects do not protect devices from EMP, it is simply NOT how EMP's causes damage.
-EMP causes damage by inducing voltages in conductive material.
a. If the voltage cannot discharge thru vulnerable components no damage will be done.
b. If conductive material can be shielded from the EMP pulse, no charge will develop and no damage occurs.
c. If a safe conductive path to ground can be provided, induced voltage will dissipate and no damage will occur (Corollary to the principle "RF gotta go somewhere").
d. EMP can't reach inside electronic devices, it can't pass thru proper shielding, it is simply the earths magnetic field acting as a transformer winding, inducing voltage.
-Thought experiment: Which radio is less likely to suffer EMP damage?
a. A radio with lots of wire, antennas, power cords, control cables, speaker cables, computer interface cables or,
b. A radio sitting on a shelf with nothing attached to it.
c. A radio sitting on shelf inside a sealed metal box
Alternative question: Which radio is more likely to survive EMP?
-A radio with a top notch no expense spared ground and protection system per Motorola R56 Standard or
-A radio sitting on a ham's desk connected to power mains, and an antenna, and a computer with no grounding or lightning arresting system.
Re-Read the basics of EMP discharge in any text book to see HOW it affects devices.
Good advice for anyone seeking knowledge on any subject matter. No need to do that however. Again, HOW EMP damages equipment is by [edit: inducing high voltages in metals/conductors and the] discharging that high voltage through the electronic/electrical components.
To highlight the futility of trying to protect a ham shack, let me observe that I spent 26 years in the Navy working in and around electronics and communications at various levels shipboard, aircraft, depot and fleet staff. We had no "EMP Operational Plans", we did NOT have "EMP reserve equipment", we did NOT have Faraday cage storage for equipment.
Our protection was good engineering practice for installations, and deal with the consequences after the attack.... b. [edit: although common sense is always good and shipboard, shore antennas could be disconnected and ground if a nuclear attack was anticipated].