arc tan cos - heck, dem are loadies, not einsteinwannabes...
Standard gear is the strap with double-stud fitting, rated at 5000 lbs ( 2250 kg ). So if you want to secure for let's say 3g upwards and you got a piece of 15000 kgs: 15000 multiply by 3 gives 45000, divide by 2250 makes 20 straps evenly spaced over the piece and evenly clipped to the seat tracks. Upwards means upwards . Too much deviation from the direction u wanna secure it for will of course lower the capabilities of that particular strap considerably. Means you will need even more straps to compensate. With loads comprising of lots of floating units ( i.e. not secured by the locks available) securing the load can take a hell of a lot longer than the loading itself...