I rode in a late model domestic convertible the other day and the "cowl shake" was horrible. It felt as if the whole chassis was wobbling back and forth. Since I have never actually ridden in my JH project, I was wondering what it is like in a JH. I am in the process of replacing the rocker panels and floor pans, so what could I do without adding too much weight to stiffen the chassis? I have replaced the floor supports with 1x2 rectangular steel and the floor pans are being made of 16 ga steel.
I've driven my somewhat crumbly pre-restoration JH for years (needs floorboards at a minimum). I've never noticed any cowl shake. In fact, the body has always felt good and solid while driving (now, mushed up bushings make for an interesting suspension...)
I've had this old car at pretty significant speeds, under significant acceleration and hard cornering.