AidenJ wrote:
My guess would be that in order for the jacks to hit you need to have lost your wheels. My truck is stock and hauls my camper fine.
While losing your wheels would be bad it's not the only way to tear out the rear of your camper by catching a jack on the ground. What the OP is referring to is departure angle. As the length of overhang increases the departure angle decreases making it more likely that you will contact the ground with the back end of the camper or in most cases the camper jacks because they are the lowest point at the rear. Uneven back country roads, pulling out of parking lots, pulling off the side of the highway all have the potential of making contact if you are unaware. This would be catastrophic to the rear of the camper.
Here is my first TC showing an example of departure angle. Arctic Fox 1150.

Here is my second truck camper( Northern Lite 9.6) so you can see the difference.

Here is an example of departure angle in action as I cross a dry creek bed in Idaho and start up the hill on the other side.


You can see the potential for damage if I wasn't carefully watching.
If a cooler is the only thing keeping you from getting a slide you could consider other placement options. My dinette will hold a 6 foot cooler when made into the sleeping position, just add a couple tie down points to keep it in place. The overhead bunk is another option because you already had to lift it up into the camper what's another few feet? I could manage a 4' by 2' cooler on the floor of my slide-out camper, how big is your cooler?
I have a 48" superhitch truss extension for my latest camper, another AF 1150. It has an 11'4" floor like the NL you mention.

Keep in mind the extension will now be your lowest point and decrease your departure angle even further. I have bottomed out exiting a few parking lots already.