Nicely done mate!
About Aperture F/Stop and the Sigma 8mm Fisheye lens. Optimal sharpness is actually between f/5.6 and f/9.5 with F/8.0 the safest bet. Finding the Hyperfocal DOF distance that gives you greatest near and far focus and sharpness will go a long way to crispy images. I have found that forgetting the onboad scale and focusing on something 1.3 meters away from the focal plane marker is a suitable set up. You can see an example of mine using a Canon DSLR and Sigma 8mm fisheye here.