This was an interesting thread. Another thing I added to the coil rack was to lay rubber straps, known to some as coil belts, across the wooden blocks in the coil rack. Protects the coil a little as well as perhaps giving the coil more grip. Several places where I loaded the coils insisted on your wooden boards being beveled. Meaning they had an angle cut. In fact, two places I can think of wouldn't load you unless you had beveled wood.
While leased to Fikes, I hauled a lot of big 40,000#+ coils. Our lease trailers were Utilitys with a 10' 2" spread axle. They had what is known as a coil package. It is extra crossmembers in a small area. They were basically in the center, though slightly aft. I enjoyed my coil hauls. I liked the challenge. Many of the coils I hauled were laying on their sides. The shippers insisting on straps rather than chains. I used to pick up giant coils loaded this way at the plant in Russellville, KY. Those coils always went to beverage plants for cans. I often hauled them to Golden, CO.