The FWC Keystone is about a foot longer than the FWC Grandby. The extra room inside is nice. It makes room for a full length rollover couch and the cassette toilet (we do not have the cassette toilet - I put a low shelf in the vacant area there and we store a pota-pottie under the shelf. On top of the shelf I secured a plastic Sterite 4 drawer storage unit from Wamart which works great for clothing on our long trips.
The camper does extend past the end of the cargo bed. We keep our tailgate on (folded down of course) to protect the bottom of the camper . The camper only extends part way across the tailgate and the ledge creates a place to set things and for us to stand on when entering and exiting the camper or when latching and unlatching the top (our vehicle is a 4WD Dodge W250 that is lifted 2" and the latches could not be reached without the rear camper mounted folding steps or a step stool if we did not have the tailgate ledge to stand on. We can reach the front latches without a step stool because I have running boards (which will be replaced soon by rock sliders).
We use a fold up Little Giant step stool to get in and out and it works nicely for us. I also added a Carefree of Colorado 'Truckin Awn' over the back door and mounted to the camper body not the roof. It is great to have in the rain! I had to fab a couple of custom Aluminum brackets out of 1/8" thick Aluminum plate to support the Awning legs but they were not difficult to make.
I hope this is helpful,
Craig
