I've got my motor pod sitting on top of this EAR product:
http://www.allsealsinc.com/1b.html
It has dampening foam seated in between 2 aluminum plates. Very hard and stable and still has some dampening and isolation properties.
http://www.allsealsinc.com/1b.html
It has dampening foam seated in between 2 aluminum plates. Very hard and stable and still has some dampening and isolation properties.