diy power cable

Try to make power cable like that:

http://virtualdynamics.ca/the-oddiophile-ep-10

I went and measured the back of Wattgate plugs, your solid core 3/8" will not fit. If remove the flat plate and insert your solid core in WITHOUT the holding screws, your 3/8" solid core still won't fit. However, you can trim the tips of your 4awg S.C off to the shape of the "entrances", push them in and screw them down.
Last time I looked at HomeDepot, they had some commercial sockets that were pretty big. You may give themt a look.

"Don't electrocute yourself or start an electrical fire"

Excellent advice and well thought out response Bob...given he's dealing with current I'm sure the thought never crossed his mind :^'

3/8" diameter solid core? I thinks thats called a rod, not cable.. I don't know of any domestic connector that will fit this, any reason for the size?

Best, P.