Here is the link I promised:
http://ecomodder.com/forum/showthrea...echo-7380.html
I certainly would not recommend the solid cinder blocks for support. My Echo was very light in back, so I was willing to take the risk, but the Camry is much heavier and much lower. Risk just to great in your case to use those supports.
BTW, coroplast can sometimes be picked up for free. It is one of the primary sign materials in political campaigns. We are in election season ;-)