I put 2 bikes behind the cab. I don't remove the wheels, I place each bike opposite the other, and I turn the front wheel. I have an aluminium headache rack, to which I tie the bikes, in an up right position.
The bikes are full size, hybrids. (Rocky Mtn 'Whistlers')
The box length overall is 8', and it's a full size Chev.
I like to be able to see the bikes.
I did opt for the receiver sleeve on the rear of our 5.TA, so that I can place the bikes there, if the need arises.