John,
if the bow support gives even a bit, the boat can ride up in front. Typical bow eyes may not hold and you never know what state they are in (I've had one snap during normal retrieval). In that scenario, the boat could slip out from under a stern strap (like the one Tim shows).
I've added a strap in the front half of my trailer that goes around the bow of the DS, forward of the cuddy. I snug the winch but also belay the painter on both the bow post on the trailer and the foredeck cleat.
I have no idea how this would hold up to a 60mph impact, but I feel it would survive a larger range of conditions than the typical front&rear.
Powerboats are often secured to their trailers with two short straps in the back. Their main advantage is that they control the position of the boat on the trailer more positively than a "loop" strap. Under a loop a boat can twist or shift during transport, because not all changes in position would result in stretching the loop. A separated pair of straps works better. (Something that I would look into if I ever contemplated trailering over longer distances).
I opt for a pretty short rear overhang, because I really don't want to have someone spear themselves on the mast. I've had one driver run their windshield right into my parked trailer - despite a nice flag, so I'm convinced people just don't see that, or can't judge its position.