I am rebuilding the sidescreen box and rear seat support for a 4 seat PB. The box needs to extend across almost the full width of the rear to hold the back side screens. The current telescopic shocks and the Hartfords take up too much space. The Luvax fit tight and low relative to the springs and rear axle.
The ones I expect to add use relatively modern steel boxes not the 1930's original pot metal, which is certainly fragile.