Agreed.
Whenever I have had the existing bus drilled out to land additional cables I have had to arrange (and pay) for the UL folks to make a trip to the field to revalidate the UL listing because the equipment had been changed from the way that it was originally tested.
I wasn't crazy about the added expense, but the insurance wouldn't have paid in the event of an incident because the equipment would have lost its UL listing otherwise.
