Rugani, Regarding your 8mm shot where the lens shade shows in the corners I will give you my take on the issue. I had the same problem with a much larger port made by Athena back when I first started shooting with the Olympus E-300 and E-330 cameras with the Olympus 7-14mm zoom for 4/3 (not M43) cameras. All of the dome shades were designed for cameras that use the 3:2 format, as in 35mm or APS-C. Since the 3:2 image is not as tall (0n the short side) as the 4:3 image the hood would show in all four corners of the taller (4:3 aspect ratio) photo. I resolved the issue by shaving off a bit of the hood. I addressed this issue with Athena and they later revised the hood so that is would not vignette with the 4:3 aspect ratio cameras.
Regarding the 7-14 zoom with the same port, One size does not fit all WELL and results will vary greatly depending on the port you use with this lens. I see people shooting macro with ports where the macro lens sits 10 or 12mm back into port to save money and then wonder why they are not getting the amount of magnification they thought they would be getting from their +10 closeup lens.
Inon makes great products and it appears that the 115 dome is an excellent choice for the 8mm but not so much for rectilinear lenses like the 7-14, 12-40, 9-18. I still think the best choices for these lenses are the ZEN 170mm port and the Nauticam 180mm Optical glass ports.
The Hammerhead is the 7-14 zoomed to 20mm at F/6.3 and the cave entrance is at 7mm and F/5.6. This lens has great DOF and I have no problems shooting in a range between around F/4.5 and F/9 all the time with executable corner sharpness. I don't want to get into yet another debate about the corner sharpness of this lens but it is as good or better in that area than any of the rectilinear I have seen tested at the 114 degree angle of view range.