Vignette-Free Dome Port for Sigma 15mm and Ikelite 200DL?

Aloha,

Can anyone recommend a dome port for the above combination that is compatible with Ikelites newer Dry Lock housings? Ive been trying to get more information on the Precision 5 port but to no availfrom what I can tell it was designed for the previous generation housings. Recently purchased Ikelites 8 dome but a significant amount of lens shade is in the frame (I have not yet tried removing it). Thank you in advanced for any suggestions!

This is from Ikelites port chart for the 15mm Sigma :

Slight vignetting (dark shadows in the corners of the image) may be present with full frame cameras. AF only.Product(s) required:75340Dome Port

The way to reduce vignetting is reduce extension but their recommendation is for the bare port. Looks like the Dry lock ports have some amount of extension built in. If you look at the Canon 8-15 they recommend removing lens shade for that lens.