My ideas on fixing rear suspension from bottoming out. Good/bad? PICS

[avalonshoe]

I dislike the design of the rear strut placement on my avalon and the newer avalons. I have a problem with my car bottoming out the rear of my car when i carry just a few light passengers and barely anything in the back. Rear struts were changed to KYBs but I kept the old springs on there. Now I have to travel with casefiles, tools, and a boat load of equipment in my car. When I do this, i refuse to take any passengers because i put my casefiles in crates and leave them in foot area of the back seat so that no one can sit there.. Also, I do this to distribute the weight to the center/front of the car.

My options are:
1. ..To find coilovers for the rear with stiff springs;
2. ...find shocks with pressure adjustment (i doubt they make them)
3. ....or to make custom make rubber bushings and insert them "evenly" into my springs to prevent them from collapsing all the way? I'm interested in this option b/c it is the cheapest alternative. Moreover, does anyone have other ideas or comments on how to prevent me from killing myself by doing this?

Sorry for the pics, it's a quick box drawing.