Osage, installed with the doors on, Its better if you take them off because you dont have the weight hanging off the pillars. You need to tie the A,B, and C. Pillars together with some square tubing running across all 3. It would also be wise to cross brace the B pillar on the Drivers to the B pillar on the passenger side top to bottom. So a large X from Bpillar to B pillar. This will eliminate any possible movement. After you tack weld the Rocker in you should re-install the doors to check for fit. When you are Happy with the fit you can weld them complete. Hope this helps. Any more Questions go ahead and Shoot.
Thanks Bob.