Nauticam adaptor for Subal dome port: possibility of vignetting?

Hi, I'm planning to switch from Subal (D700) to Nauticam (D750) system. However I would like to keep using my Subal 8" fisheye dome port if possible.

Does anyone out there got experience using the Subal dome port on a Nauticam housing via a Nauticam adaptor for Subal port?

I believe the slight extension won't affect image sharpness as such. However my greatest concern is whether there's any vignetting with the slight extension from the adaptor ring.

Any input is welcome!

I've been using a Subal/Nauticam adapter with both my 8 inch Subal dome and 4 inch Zen Subal mount dome for over four years with no problems. The adapter does not add any extra extension, it is designed so that it positions the dome port and Subal recommended extension rings in the correct position relative to the lens just as it would be with a Subal housing with the same port/extension ring combination

Thanks for the helpful & reassuring info! I just took a closer look at the pictures of the type 3 & 4 adaptors and now understand what you mean - the design is really good.