We start with an old Army blanket covering the back floor. Rear seats folded flat, of course. Front wheels off the bikes. One bike goes in left pedal down and handlebars first, pushed against the port side of the car. Another blanket, then the second bike left pedal down and tail-end first. This leaves 12" - 18" on the starboard side for two large suitcases and numerous holes here and there for helmets, backpacks, and other small items. The front wheels top off the load.
If we plan to leave the bikes in the car on an overnight stop, we cover the whole thing with a cheap black velour blanket. Seen from outside the tinted windows, the load disappears completely.
I still have the view--such as it is--through the back window. HTH