At the moment it's edge to edge with the zip, so you'd need to cut it as if you're adding buttons and buttonholes...so you'd need to add an overlap.
I've just had a look in my box of strange, obsolete, weird size/length zips to see if I've got anything in there. I've got a few 5 inch open ended zips, but I've also found a baby pink zip which measures 7 and three-quarter inches long. What colour did you need? Is this any good for you?
Sandra.
xxx