Can anyone recommend a source for extra-soft/flexible body mounts? I'm replacing the bed on an '81 with a camper box made of wood, and want to lay it on soft mounts that'll absorb flex, to prevent the box from cracking. I need them to be about 35mm (~1.5") tall when compressed, maybe a little more.

I've used fluid-filled motor mounts on various car projects, and I like them a lot in spite of the price. Anyone have experience with this type of body mount, as far as ride and reliability go?

I did a search but all I found was info on lift kits and mentions of polyurethane.