Best extension for Sony+MC-11+Canon 8-15mm with Zen mini dome?

After watching Alex Mustard's excellent WAM (WideAngle Macro) Reboot masterclass last week, I got really excited to try having a go at it. We don't get too many big animals here in Chile, so this could provide an alternative with local diving until travel resumes. 

I currently own a Sony A7rIII which I use with a Sigma MC-11 adapter and a Canon 8-15mm Fisheye. I use the Nauticam 30 extension when using this combo on a 230mm dome, and was wondering if I would need this one, or any other extension, if I used a 100mm Zen mini dome?

Any help would be much appreciated, thanks.

The port chart shows that with the 35.5mm N100 to N120 port adapter the Canon port chart applies with a Metabones smart adapter - this is the straight adapter without glass - the Sigma MC-11 I assume is also a straight adapter with no lens elements - in this case they MUST be the same length so the same extensions are needed.  The 35.5mm adapter is effectively equivalent to having an EOS body in a Nauticam housing with the adapter flange at the same position that the camera body flange would be.

It follows that if you use the Canon Nauticam port charts with the 35.5mm adapter you also use the Zen Canon port charts which is here:  https://www.portchart.net/zen-only/by-combination-group/nauticam-n120/

According to this no extension is needed with the N120 100mm dome.  This is the DP100-N120CR dome and if you look at images of this dome it includes some extension with the dome:  https://reefphoto.com/products/zen-dp-100-n120cr-4-inch-glass-dome-port-for-canon-8-15-nikon-8-15-nauticam-removable-shade

If you use a different version such as the DP120N version for Nikon 10.5mm for example it has no extension.  In this case you would need to confirm how much extension is built into the N120CR version and match that.   Zen have a support contact page on their website where you could ask.

No extension required with the n100-N120 port adapter snd the 8-15 works well with both MC-11 or Metabones.

BE AWARE, Zen has different versions of the N120 100mm dome port. You need to be sure you get the one with the removable dome shade, the non removable shade will vignette towards the 8mm end of the lens.

You can read my review for this lens with the Sony A7R II in issue #93 at uwpmag.com, this is a free PDF download.

Yes, thank you both, I just wanted to make sure. I am aware I need the one with removable shades, thanks again.