I love the ability to overlay text from an image exif properties. My suggestion is simple I think. I am typically batch adding gps text data in the lower left corner of my images. Some of my images are cropped which results in the overlay text being much larger. It would be nice to have the text always be the same percentage of the image's total height. Maybe add a field to specify the percentage of the images's height you want the text to be - possibly with a range of 0.1 to 10% of total image height