5 stage vetting I would always recommed.......
although be aware soem of the things you have pointed out certain vets may fail the horse for (to cover their own backs mainly!)
you posted before about the tail..... I think that is a make your own mind up, and ask the vet on the day of the vetting about it etc....... I definetly think you will get a chunk of money off for it though as it is not a "normal" position for the tail to be in and could indicate an underlying problem.....
i agree with the signing of everything etc, and would possibly ensure that you note down on the form the owner will sign all the past history stuff as well so she signs that that is all and everything etc.....
part of a 5 stage vetting is watching the horse be ridden..... ensure that this is included as horses often act differently trotted up, turned in a circle, ridden etc..... and then ask the vets opinion on whether any of this stuff will effect the horses ability as a show jumper. Ensure the vet knows that this is your intention with the horse!
good luck