It has been quite a while since I spent some summers logging with my Dad's company in N. California. If I recall correctly, the custom and practice was to tie two wrappers to the bunks and then some more around the load. They always tied the load down on the landing before moving the truck down the hill, or up depending on the terrain. Yes, they stopped at the highway and checked how tight everything was after a few miles of driving. This was back in the early 60's, which might tell you how old I am.
As for lowbed tie down practice, it always seemed like enough chain, but never really asked a driver what capacity they were aiming for. Biggest thing back then was probably a D8, or a shovel converted to log loading, like a Northwest Timbermaster. This was all on conventional highway trucks, so the blade on a D8 was usually separated from the tractor.
