All you have to do is that last strap differently and it's all good. I teach this method to every Basic class. Preferably above the kneecap, put the 9-foot strap through the handold, over both legs, and into the opposite handold. Cross back over both legs, around the feet, and back over to meet the buckle and tighten. The patient can now be stood feet down or head down and they WILL NOT MOVE.
It can be done below the knees for tall patients, but I prefer above as this will leave them incapable of bending their knees and therefore kicking out of the strap- great for combatives!