rust repair questions....

[72gmcshorty]

i want to start tearing into the rust on my blazer and looking for some advice. I need to replace the rockers of course and whatever rust damage i find underneath. I still have the top bolted on. Once i remove the door, will that be enough to keep the tub from flexing or should some more reinforcement be used? On the passenger side, the door lines up pretty close already (the floor is not rusted out). The drivers side floor and rocker is pretty much gone and the door sags alot. How do you get the tub back to its proper shape? i've also checked out the rocker replacement thread but that for a truck not blazer