One of the problems is it can be difficult on some vehicles to find a convenient place to tie a bow/stern line to the car frame.  What I have done on the front of two vehicles now is get a short (18") piece of wire covered with a plastic coating, get a doo-dad that allows me to turn it into a loop, and I attach to the frame in the engine compartment.  I have enough clearance in the seem of the hood, that when I want, I can extend the end of the loop through the seem between the hood and the fender.  To tie down the bow, I just tie the bow lines to that loop.  (Under normal conditions, the loop just sits inside the engine compartment, out of the way of anything.)