A little absurd, but since we've never found a bike rack that fits, I've started taking mine apart to put in the boot. For a 56 Specialized "compact" road bike, I remove both wheels and seat post. "Hook" the bar over the bulkhead, so that one dropdown is in front, one in the main compartment. Depending, I sometimes need to fold up the rear derailleur to get it over the transom. Then, both wheels are laid on top, hatch closed. It's actually very easy to do, now takes me about 1 minute, and I don't need to worry about locking anything, besides the car.

A few things to watch. First, the plastic on the top of the bulkhead will get rubbed, sometimes by the metal front brake-be careful not to scratch the plastic or use a towel. Second, if you have a computer sensor on the front fork be careful. Location of mine casues no problem, YMMV. Last, depending on your bike hygiene habits, the derailleur and/or chain may be greasy, careful where you put your hands, a rag helps. I've put a piece of tape around my seatpost to easily find the right height for re-installing.

Again, it's actually EASY for my frame, and much better than nothing