I have a standard bed camper (approx 6.5 foot) on a long base truck with a combination fuel tank/tool box in front of it. The camper is 21 inches away from the font of the truck bed. My COG (center of gravity) for the camper is about 3 inch behind the centerline of the rear axle. I had this same setup on my old truck without any weird effects.
My fuel tank/tool box weights between 200 pounds and 700 pounds depending on fuel level. That 200 to 700 pounds in combination with the camper has an effective COG that is still ahead of the rear axle. This combination has been all over western Canada, Alaska, and western and midwest USA.
LeRoy
Homeless by Choice
FULL TIMER since 2012
2015 Chevy 3500, Duramax, 4X4, DRW, Crew cab, Long bed
2013 Northern Lite 8'11"Q Sportsman truck camper
2015 Polaris RZR Side by Side