When to Weld in Frame connectors

I would put the jack stands under the frame in the spots that are flat, like right by the front spring hanger and right before the frame bends up for the front suspension. Check to make sure your doors still open and close smoothly. The gap is still the same around the doors and the car is level all around. Now you can weld them in. Thats how I have done mine and never had any problems.