We are currently using lifting slings to lift a load from a palletised crate onto a bench via a forklift. The load is awkward and we must use a FLT for the puprose. The load weighs approx 450kg and I have purchased 4 off 1 ton poly slings which will be used in a 'choke' hold at each corner, looped through a suitable lifting point on the frame of the load. Given the set up of the load (choke) I have reduced the SFL to 800kg (0.8 x SWL=800kg). Someone asked me, because we have 4 slings can we lift 4 times this SWL? I said no because this exceeed the SWL of an individual sling, however, I dont know the 'mechanical' reasons behind this - am I correct and why?