Pop the rear window and run some rope or bungees around the frame and secure it under the rear somewhere.
You should be fine as long as your not driving long distance or on the highway.
2015 Altitude - Billet Silver II
Tow PKG + Park Sense + Backup Camera + Navigation + 9 Speaker Audio
Mopar slush mats, Mopar 4" Chrome tips, 1.25" Boras, Gorilla Black Lugs,
15% Tint Front Doors & Visor, Polk Center Spkr, Sylvania Ultra Lows & Fogs
Previous: 2008 WK 4x4, 2014 WK2 Billet Silver Altitude: Lemon