Hi, Uprights are always power hungry compared to the Chest type Fridge.
Every time you open an Upright, you let ALL the cold air out.
Chest types always hold a greater portion of the hard won coldness.
Up to you how you do it, there's always a drop slide.
You would need a vehicle with Barn door, or side swinging doors, for a drop-slide to work.
Especially if you fit the slide to the floor in the rear of your 4x4, and squeeze in a couple of draws beside it.