Hey Scott, nice job there. I would like to make an observation here if I may...
I am a Calif. truck driver, having hauled alot of coils in my time so, please bear with me here.
1) the coil should be turned 90 degrees so it sits across the the 2 frame rails down the center of the trailer. To prevent falling thru the deck.
2) Some people like to build a "cradle" for it to sit in which helps hold it in place. Personally,
I used 4x4s running crossways one infront & one behind where the coil touches the deck with the coil ontop of them (like chocks)
3) depending on the size of the coil, dictates the # of chains required.
under 10,000lbs 2 chains 1 pulling to the front, 1 to the rear.
Upto 30,000lbs 3 chains 1 to the front, 2 to the rear.
upto 50,000lbs 5 chains 2 to the front 3 to the rear.
as for a tarp, you can use a damp paper towel and drape it over the coil.
Hope this helps.
Eddie