Still working this issue through. Have discovered that some of the heavier IEC cables (14g and 16g) do have very positive and large mating surfaces. Not as firmly in place as the PowerCon, but electrically good, and better than all those I first tested.
Received a couple of the IEC cables from Canada that can not be removed without pushing down the tab. They are nicely made. Good heavy wiring. The way they hold on to the IEC jack is that they have a metal edge that jams onto only the center ground tab (remember a Chinese finger puzzle - the harder you pull the more it grips?). That is a great way to keep the cable from being inadvertently pulled out, but it is only hanging onto that ground tab. Nothing else. And. . . there is no wire more important than that ground tab for all of our safety. If it gets strongly pulled it can (depending on the IEC jack quality) break that center ground pin. Probably not something that will happen frequently, but electrically these cables are the same as any other decent IEC cable.
I continue to test (and ship) the greatly more robust IEC cables with all 700 watt products.
And to see who is reading to the bottom . . . I received the first 25

M700 Stand-Alone Amplifier chassis from the Metal House yesterday. Now they go for silk screening.