Well. What a crummy design.
If the flat spring were on top of the draw bar, the top section of the flat spring would definitely be in contact at all times with the bottom flat edge of the rear of the cab itself. So, why wouldn't that work?
I mean, the horizontal bar underneath the cab is screwed right to the underside of the cab. Wouldn't direct contact by the spring with the cab itself be better?
Mannyrock