Less than 4’x8’, more like 3-1/2’ x 6’. Roughly 20 Sq ft. What kind of solar generation are you going to do in 20sq ft? Not much. That’s like 9 PA els, at 100w each under ideal conditions.
Once you start doing your own math for your own camper, it suddenly becomes painfully clear how limited solar still is, even with lithium batteries that weigh half as much as a lead acid, and store twice as much energy.