The strap is to support and adjust the incline of the seat, not to keep it from flopping forward. The seat should not, I repeat should not be resting on the rear bulkhead. If it is resting on the bulkhead it will cause the seat pan to crack, because it is not designed for that kind of stress. I have repaired several over the years. Some of the early airplanes had issues with the straps and adjusters slipping. For those a half hitch knot in the free end of the strap helps. Also you have to watch the positioning of the adjuster, because of the angle an placement can cause it to release when you sit in the seat.