think your Problem is the port Adapter, because it give you more lenght.
I have a Zen 4" for my Hugy housing, and there is one for the Tokina 10 - 17mm and another one for the Nikon 10.5mm.
With this small domes, there is nearly no tolerance for sharpness.
If you wanna use it with the TC, it might work, depending on the lenght the port Adapter is adding.
Have the same Problem with Hugy housing using Nauticam macro port and Athena dome port.
If i have some time, i plan to start a list with housing brands and measurements of bayonett edge to housing edge, to make it easier for People using different housings and ports.
- Anders Nyberg likes this