When the PO put the C4 in,he drilled the two holes for the C4 mount into the top rear of the crossmember, which was a bit too short of a distance, binding it. This caused it to tear the rubber cushion from the steel mount.

What I ended up doing was turning that mount upside down and welding it into the top of the crossmember, then gussetting it for strength.

Here is a pic that gives you an idea.

 

Thank you, this very helpful and hopefully will prevent me from making the same mistake as the PO :-)