Ignore the rear sag, it's the weight being taken off the front wheels you need to be concerned about. That reduces steering control. The trouble with these small SUVs is their soft suspension. It's made for a comfy ride, not taking on a load. I towed a '93 Jayco 1208 with a '92 GMC Safari. I didn't fully understand the dynamics of towing back then and hated the loss of steering control.
You might check the owners manual if you can get a look at it, most pop-up frames can't handle the stress of a W/D hitch. As said above, "careful" loading, that is put your heaviest stuff over the axle and move some things to the back to take some of the weight off the tongue. But don't take off too much, you still need at least 10% on the hitch for safe towing.
2013 Jayco Jayfeather X20 E, 2008 GMC Sierra 1500 Crew Cab Z71 SLE