Urgent Outer Arch Question (with pictures)

[Give_Me_Spices]

Hi All,
first, thank you for all your help thus far. The work on my dome is moving along, unfortunately as I'm doing everything by myself I seldom have the opportunity to take photos. I do promise to do a photos/lessons learned post when it's all over.
Today I do need your opinion urgently regarding the outer arch, which is next on the schedule. So far I had envisioned it to have a single brick wall ( see the Original Design.png attached). As I just finished the dome I started considering doubling the wall ( see the rest of the attachments for a visual) to ensure that the arch will be able to carry the weight of the flue. I should have tied the inner arch ( the one that crosscuts the dome to the outer with a couple of bricks but it's too late now. Here are my questions to you:
1. Should I double the wall of the arch?
2. If I were to double the wall should I insulate it with the Ceramic Fiber blanket and Perlite of should I leave it as is?

Thank you in advance for your input.

All best,
GMS

[JRPizza]

It took me a minute to figure out by "doubling the wall" you were talking about buttressing your arch. With the non-hemispherical arch you have chosen I believe most builders do buttress the arch to handle the side loads. My arch was a semi-circle so I didn't think I needed to add additional support, but if you search for "buttress" you will find lots of discussion and some pics to see what others have done. Either way I don't think you need to insulate the vent, especially if you are going with the igloo look. If you build a dog-house style enclosure the vent will be surrounded and insulation could be added without changing the look but probably still not needed.

[Give_Me_Spices]

Thank you, JRPizza.
I thought my images would compensate for my lack of jargon.

Your quick input was very valuable.