Package tray repair

[Paul Philip]

I have proceeded to reinforce the package tray.I have the 3/8" holes drilled in the corners,ready for the flat steel stock.The window is out and 13 1/2" lengths of wood are in place to maintain window opening.The weight is off the corners by placing the prop at the front of the top and the bottle jack is in place.The question is how do I know when the package tray is in its proper position to cut the slot and weld the steel stock? Any help is appreciated.Paul
Dave's answer to this question is to set the window back in the frame to square the frame and jack the package tray to achieve this.