You're absolutely correct
on everything. That excellent specimen of the HOOVER Convertible, (commercial)was the "alternative" to the convertible with the headlight. As you know, the 57 was the "debut" of the Convertible. Indeed, they warped like crazy, until HOOVER changed the formula for the hood. Every hood design had a no light option. With the exception to redesigning the base of the hood, (to fit the plastic base), you can find that hood on the last of the Convertibles, (ie: Runabout). Not the nicest design, but, that commercial is one of my few, remaining "must haves".