What is the maximum angle recommended for tiedowns securing cement pipe loaded crosswise, relative to the deck?

If the first pipe of a group in the top tier is not at the front of the tier beneath:
Attach an additional tiedown that runs rearward at an angle not more than 45 to the horizontal when viewed from the side of the vehicle, whenever practical.
Pass tiedown either through the front pipe of the upper tier or outside the front pipe and over both longitudinal tiedowns.