Remember that these larger campers also have larger tanks. Filling up 60 gallons of water is around 500 lbs that just ate away your payload. My triple slide camper is typically loaded around 6k lbs and I easily have 1k lbs loaded in my utility boxes on the truck (which you do not have).
My AF 811 was typically loaded around 4k lbs, but was 2.5' shorter than the 1140. You may want to look at the 990 or an older 992 which would save you some weight. Host also makes some smaller dual slide models that may give you more room with less weight.