Fits perfectly.
Sheri - There is no danger to have the compartment door off. I choose to have mine off all the time actually. Of course, if you had to lug a massive item in your trunk with the tailgate open and it was pouring rain, I would definitely put the cover back on.
Installation is very easy. There are four screws connecting that white plastic fuse box to the frame. Just need to remove those, (don't worry, everything is harnessed in there quite securely) hold it out of the way, slide the box in, replace fuse box.

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