In reply to gearslave: The point about 'ziplock' buckles is that the are not designed to be undone.
First, that means the straps need to be long enough that the harness can still be put on over the hips easily by someone at the larger end of the size range. It is definitely the case that more spare strap is needed for than than compared with a traditional harness where the waist belt is wrapped directly around the waist. If the manufacturers aren't reasonable generous then they lose the purported advantage of the harness being quicker to put on. Therefore, in all harnesses at the lower end of the size range the straps are excessive.
Second, the straps on ziplock type buckles have doubled back ends. If you cut the straps without replacing these, the buckles would undo pretty much every time the harness was taken off. Since the buckles aren't designed for this, re-threading them is much more awkward then normal buckles. As such, the harness would be a pain to use and you would have the worry about the possibility of loops completely undoing.
As such, if someone did want to alter a WC harness they would really need to visit a cobblers to get the straps professionally shortened with new bar-tacked ends. If that doesn't constitute a design failure, I don't know what does.