Forgot to address your additional questions about the DiamondBack.
Loading and unloading is not difficult, although it might be a bit concerning the first couple of times. The bikes are up there, but it really isn't that bad. The 12' folding ramps are very secure and are "locked" in to the frame rails so they do not come off and no need to strap them down. The ramps have extra high sides to help keep the tires tracked. I'm not certain the ramps would keep large, deep lugged tires tracked but you would feel the tire start to lift if it were climbing the side ramp wall. I've never had that happen as I'm very careful about properly lining up the ramp and staying straight while driving on/off.
I went with the ramp rails on the sides and back for options to load a single from the back, or two from the side. It's a good system.
Once loaded, my truck does not feel top heavy at all almost like the center of gravity did not move. Truck is a 1-ton SRW Diesel CC LB and feels equally stable when towing my TT and Grizzly loaded on the tonneau.