Thanks Charlie, Thanks Dave,
Charlie, the problem isn't the sitting... It's the getting back up after sitting for a while...
And Dave, the original plan isn't what I want to do but, when it works out to be the only option, I guess I have to run with it. Building the foam core brackets yesterday commited me to that plan though. The only other place to put it was in front of the right rear tire but, sinking it into the floor would block the route for exhaust.
It just amazes me that, even though this is a van, there is no room for anything when you start throwing big tire and motors at it....