I always use a cable on the winch, the strap is junk, and if your in salt water it will rust your winch to junk in no time!! I also WD 40 the winch cable, hook and winch after each trip just to keep from rusting.
safety chain from bow eye to stop, is a must! you are right you don't want to look in mirror and see boat sliding the the road behind you!!
when i had the V i use to transom strap it to trailer, belly strap to much trouble and the boat heavy enough to not bounce off. just don't forget to take them off when putting boat in water! I watched a guy yelling and screaming one day at the ramp he couldn't get boat off trailer so he pulled it out and saw straps, was funny site!!

I initially used a strap. Even as thick as it was something kept telling me don't depend on it.
http://i175.photobucket.com/albums/w...trailer003.jpg