[Plugin: NextGEN Gallery] Properly generating cached thumbnails for singlepic directive

Using NextGEN Gallery version 1.7.3 I had an issue where the plugin wouldn’t create thumbnails in the cache directory. I.e. my settings would specify 100px X 75px but I would get something smaller than that, but I needed them to always be the dimensions that I specified. I was able to achieve that but only after changing the code in image.php file. I wanted to find out if

1. Is there another way to ensure that cached images are of the size I have specified?
2. If not I wanted to contribute the changes that I made to the project so that they can be released in the future version of this awesome plugin. Is that actually possible?

Thank you,
Anton