loose IEC power cord connection?

Rrog, agree with you.

My Conrad Johnsons ART preamps (at least the series 2 and 3) came with hardwired cords. At 16,000 and 25,000 dollars, I don't think they were trying to save a few dollars by doing that. At least they have hospitol grade plugs on them.

Best method I found was fitting a piece of black heat-shrink tubing over the IEC plug.

Black "electricians" tape is all you need. It's so bloody easy...just wrap a couple turns.

Nothing applied to the outside of the IEC plug does a thing to improve its connectivity. Just keeps it from falling out.