How fast should one drive a similar sized delivery truck?
Don't some states require delivery truck drivers to have special skills and a special license?
Class C owner-drivers don't have to (legally) have any special skills or a special license. That tells me that Class C motorhomes should certainly not be driven any faster than a similarly sized delivery truck. Since most of us Class C owner-drivers probably have not logged the hours that a delivery truck driver has - who does it for a living - then we should maybe even drive at slower speeds than a similarly sized delivery truck.
I would LIKE TO DRIVE my Class C at no more than 55 MPH, but unfortunately other drivers usually won't "let me". I consider it a good trip if I was able to drive our Class C at between 55 and 58 MPH on the open road without doing emotional or physical harm to myself or others.
P.S. I can drive our Class C at 75 MPH. However, I try not to conduct my life based on what can be done ... but by what should be done for prudence, or other, reasons. :)