The NEVCO manual gives you the instructions (top and bottom vent settings and times) for strawberries, jerky, fruit leathers/roll-ups. Watermelon might be a problem - depending on how thick you slice it - but you might treat 1/8th-inch thick slices like pears.
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain