And it sounds as if you want to increase it, because when the height is about 9300, the rendering has been scaled down to 2000/9300.
If you really want to have only a single image, then you need to make the tradeoff for your app how big an image you can afford to render and how big your users would want them to be. For example, a 10000x10000 image would require about 400MB in memory.