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I totally understand the Mothership's response. They cannot support every Egg configuration so they have a standard and the Rutland gasket isn't part of it. Having typed that, the OP will most likely have the same alignment issues with the standard gasket as well. Loss of support (to some extent) is the risk we run from using "non approved" materials.
@dagriller - I was going to recommend exactly what you posted about switching back to the supported gasket. In IT, we have had to do something similar to a system before to get vendor support. Then, when you have the same issue, maybe they will move on the other solutions. I had an alignment issue on my Egg which I lived with for many years until I replaced my hinge/band assembly. I found having the hinge up high in the back and the bands low in the forn fixed my underbite issue. Good luck.
Dealer can tell you SOL but the Mothership will rule. They can hook you with another dealer if necessary.