Crazy,

Here are a couple of pictures of the firewall I use with the 30-10 Evo motor, very simple, just 1/8" lite-ply with carbon laminated to each side. You have to use a backing ring for the bolts or they can easily crush the firewall, so 2mm solid carbon, or 1/8" aircraft plywood work well. The ring just needs to be big enough to support the washers on the bolts. As shown this firewall weighs 22 grams.

There is no need for a softmount with an electric motor, just extra weight and expense that is not required.