No stock Ford E350 handles cross winds or big trucks going by like a stock Chevy 4500 chassis in my experience. Both were about 30’ overall.
Both rigs had all the water tanks over or just behind the rear axle. I am surprised some manufactures place the water tanks at the back of the camper. My two class Cs have had that room for storage (almost 100cuft). I doubt I have anywhere near what water weighs back there.
But I do dry camp with electric most times. I can go a week with or without electric. Depending on the weather.