Loadmasters and mechanics have no duty time limits, sometimes they are on the planes for as long as 5 days (I have worked for several cargo outfits).
I have flown the smaller MRAPS. The problem these have (and you can see it in the pictures that after they are driving onto the pallets, only a relatively small stack of wood is placed under the differentials, then the tires are deflated and they are being chained down. With the weight now centered in the middle, the chains will start to bow the pallet and they will not move unless the middle is right overtop a pdu.
The large Cougar actually has 2 stacks on top of a piece of wood that spreads the weight a bit more, and another stack under the middle. Not many chains to hold it down though. After the accident vehicles had a lot more chains tying them to the pallets.
By center loading you strap / chain / net the cargo to a pallet, after that you use straps to attach to the load and into seat tracks or other tiedown spots.
After the accident I have seen new guide lines where straps can only be used for 75% of their rated capacity, 2G up / down, 1.5 G forward / aft. Angles come into play now too. If a strap is put under a 60 degree angle, only half of the force can be used horizontally, 90 % vertically. under a 45 degree angle it is a 0.7 factor. A 5000 lb strap X.75=3750 lbs x.5 (a 60 degree angle)=1875 lbs / 852 kg horizontally, and 1534 kg vertically. Most straps are angled, since it provides both vertical and horizontal restraint (stright up does not provide for horizontal). You can use a strap from the floor up, through a ring and back down into the floor. Now supposedly this one strap counts as 2, something I don't agree on. If this one strap breaks, you lose 2.
The flight crew on this flight most likely checked the load in Bastion. Eventhough it was not written in the manual, it was a common procedure. All these guys had a cargo background. The assurance from the loadmaster that he replaced a strap and re-tightened everything should have been enough for most flight crews.
When this plane rotated something broke, most likely the floor or a seat track, a piece of cargo slid back ripping the wires from the data recorders and knocking out the 3 hydraulic lines that come together at the same point. On the video there is a stream of fluid coming from the tail, clearly visible.
I would really like to see some info on how much force the seat tracks are able to withstand, and the how much force the attachment of the seat tracks to the floor beams can withstand. It is not just the weight of the cargo, also how much tension there is on the straps. Unless you run into serious turbulence, the cargo causes little stress on the straps, even at rotation. However all the tightened straps pulling up on a seat track mounted to a few floor beams might be something no-one has ever thought about.