do full frames stop body stress cracks?

[KB Camaro]

i have a 67 camaro with subframe, sub frame connectors and a 4 link and i keep getting body cracks at the end of the drip rail in the rear quarter panel. I've had weld dripped in the crack and the area body worked. it has since come back and another shop told me a solid frame would solve the problem since all the stress and TQ would be on the frame and not the center of my uni body camaro. any feedback is appreciated.

[JustJohn]

Probably someone who has actually worked on one will chime in, but speaking strictly from an engineering load analysis, if you move the cyclic loading (flex) to another point in the structure then yes it will solve the problem.