I have looked at the issue from a few different angles (pun intended) and I believe that the heavier E55 style mounts would hold up better if they were filled, but I also believe they will hold up better over all with the torque that is produced by the SRT6 engine.

The stock SRT6 mounts are extremely thin in the area anchoring the center post to the outer base. Even if you simply drilled, drained and filled a new stock set, they WOULD fail. They are just not thick enough to take the abuse. Plus there is no mechanical alternative in the event of failure.

It IS possible that I just did not get a proper bonding to the center post rubber that remained, but I suspect the torque is exceeding the shear strength of both the rubber and the polyurethane.

I will tear down the original mounts containing the polyurethane and see what I can come up with regarding a physical backup anchor. My first thought is a crossbar type solution, but I'll make a few sketches and see what I come up with.

In the mean time the heavier mounts are holding up fine.