Fisheye lenses are cumbersome.
The Inon with dome weight around 400 grams in water you do not want to be screwing and unscrewing such a heavy lens during a dive it takes time and ruins the thread
Bayonet mounts are better I recommend an LD mount as it is designed for 28mm or failing that an AD mount.
Weights of lenses with dome underwater
Inon UWL-100 28AD 400 grams
Inon UWL-H100 28LD 500 grams
Inon UFL165AD 85 grams ---> best
Fix 28M52 165 grams + step ring 35 grams total 190 grams
If you want to have an M67 the best option is the fix but still this is cumbersome taking on and off the lenses will ruin the thread
I have done a few tests here http://interceptor12...ots-and-lenses/
I am going to do an update with the UWL-H100 28LD as I did not have it at the time. I expect similar performance than the 105AD and of course no vignetting