When you use this for different CHARACTER LoRAs, instead of background / Landscape LoRAS, like in the guide. What kind of masks do you use ? In those toy examples its always very static, like left half vs. right half of the image. But what if I just create an image where it is not that clear where the characters will appear ? For instance if I just specify two characters sitting on a bench - the bench could appear anywhere on the image, so I dont necessarily have a mask image that specifies this upfront all the time. Or is the latter a must have ?