I don't know whether the thousand-character script you are talking about is Ou Yangxun's running script thousand-character script or lower case thousand-character script. The font of his running script is not small, and the running script written by calligraphers is generally much smaller than this. If you want to write something bigger, you can't enlarge it. If you want to write something bigger, there are Chinese copybooks such as Huadu Temple, Yugong Monument, Jiuchenggong Monument and Huangfujun Monument.