Hardy & Butler.......

The Hardy cars (forget which years) that had the mandrel bent frame kick-up "joints" 2x2 main rails (instead of miter cut/welded joints) were damn interesting from a "flex" standpoint back then. The fact that these rails were 2x2 and not 2x3 tubing would lead to a little more flex as a whole. And a mandrel bent joint will flex more than a cut/welded joint, giving Don in effect a "choice" of where he wanted it to flex more/less.

 

Even if he did focus more on the ladder bar, one Hardy 4-link car that was supposed to work pretty good was the Roy Hill red/white Capri (back before he went to the Tempo/Topaz cars).

 

 

The Butler cars were damn interesting too. If I remember correctly he said in a magazine article that his design used the main hoop as if it was the structural "peak" of the assembly carrying all the "downward" load of the rest of the chassis (or something to that effect). I think that's why some (if not all) of his cars had a door bar placed very high in the car.