I have only one mid carat, rear facing seat, .., the other I removed and then lost.., 

Anyway.., since the vanagon isn't as spacious as a larger american van.., I'd like to make every inch count.., 

For instance, for under the drivers front seat.., one of those 14X9 (ish, thats their approx size) black trays with seperate compartments from the Container store works for me.., they have different sized cells depending on which tray you get.., (the other front seat is where a massive ac/dc converter sits.., 

And under the rear bed seat.., if you have four jack stands as I do, and you remove the notched black part, you can let the red stands stand upright under the rear seat and be able to close the rear seat (the notched part lays horizontally behind the two upright stands...) [I used to not take them apart and would lay them on their side., and that was more of a pain.., ]..., this is on the passenger side.., for the driver side.., I plan on putting a propane heater (propex I think.., whatever its called..).., which is going to force me to put my gas can somewhere else..., 

But for under that carat mid seat.., I don't know what to fit or put under there.., I run with the seat never folded up.., everything I've tried to put there doesnt fit...,