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
SRT Rear Springs, Taillight Bezels and Grille Mesh, Black Gorilla Locking Lugs,
Mopar 4" Chrome exhaust tips, 1.25" Bora Wheel Spacers, Sylvania Ultra H11's,
15% Llumar Tint, Polk DB Center Channel, Mopar All Weather Mats + Cargo liner