Cropped Thumbnails (gridsquare)

I am using the General Calendar shortcode template and the tooltip images are cropped even though they are square images. The images are coming up 391×260.

Searching though the code I found the section in render.php that sets the variable for gridsquare to this size, which in turn is used by the General Calendar template.

My question is how can I change this to be a square value, or not be cropped and not have to worry about it resetting after updating. The thumbs look awful when cropped, and I wasn’t able to figure out how to fix it with css.

Thanks!