Most IEC plugs are tapered somewhat and are usually too long. The Marinco plugs are this way, as are many others.
What I have done on most of my cords is cut or sand off 1/8 to 3/16 inch of the plastic end. The internal prongs will now contact further in on the chassis socket and the larger part of the taper will make a tighter hold. This takes a little work, but it is permanent.
The 20 amp pieces are the way to go, as mentioned previously by another member, but that requires even more work, and an adaptor for when you want to try other cords.
Ril
What I have done on most of my cords is cut or sand off 1/8 to 3/16 inch of the plastic end. The internal prongs will now contact further in on the chassis socket and the larger part of the taper will make a tighter hold. This takes a little work, but it is permanent.
The 20 amp pieces are the way to go, as mentioned previously by another member, but that requires even more work, and an adaptor for when you want to try other cords.
Ril