In reply to:

So I modified the RCA plugs at the head unit end to incorporate two flying ground leads to which I soldered eyelets to and then bolted them to the new ground connection on the back of the sled.

Could you explain this sentence to me again? I'm suffering from what sounds like exactly the same issue, but I can't figure out what this sentence means. Are you saying you have permanently connected the empeg to the sled? How do you take it out of your car? Perhaps I'm totally failing to understand. I guess I don't know what a flying ground lead is, as opposed to a regular ground lead.