Yeah, I think the paper overhangs the cookie too much to just pipe a border. (The edge/overhang is irregular, so anything piped on top right now would likely look irregular too, or the borders would hang strangely off the cookie where the paper overhang is large.) I think all of the papers should be trimmed back. But that will be harder to do evenly now that paper is attached, so, once trimmed, you'll probably want to pipe borders to conceal any uneven trimming. My two cents. Best of luck.