It sounds like you already know your issues... Fisheye is bad. If you HAVE to use it please do so with lots of overlap. The GIT cameras are not great quality either. I would suggest getting some new gear if you are going to get into mapping more seriously. Maybe look into getting a flattening lens for it to get rid of the fisheye.
Also, give your overlap report a look. It has a lot of areas of light blue and green as well as some holes. Consistent overlap makes maps better. If you care about he quality of the elevation related data products you want the entire overlap report to be dark blue in the areas you care about.