Insight into dome placement onto the base

[RADG24]

I'm currently in the process of building a 30 inch homebrew cast oven.
I've built the dome separate to the base and plan on transferring it over once it has fully cured.
The base is 4 inch thick 5:1 perlicrete and will have fire brick sitting over it as the oven floor.
My question is around where the dome should be placed onto. Is it best for the base to be placed onto the firebrick base (stopping me from being able to replace the covered bricks), perlicrete base or an added outer layer of something entirely different?
Any insight would be greatly appreciated.

[UtahBeehiver]

What is your structural base? 4" 5-1 perlcrete in an insulation base not a structural base. Typically a 4" concrete structual base with appropriate rebar and/or wire mesh is the structural base then the insulation with fire brick on top of the insulation base.

[david s]

You will need to leave enough room in front of the oven to build the gallery, so don't place the dome too far back, but leave enough room for the over dome insulation layers so they don't go over the back edge.

As the drawing indicates there are pros and cons for either A or B. Dome on top of floor means the bricks uat the floor perimeter nder the dome will be almost impossible to remove if replacement is required. But it's the centre floor bricks that take a beating so the outer ones never need removing. I've never seen the outer bricks with any problems.
cutting bricks to sit inside the dome is pretty difficult and time consuming. Some folks believe that a slight gap between the dome and floor allows expansion movement of the floor bricks better, but as the floor and dome are heating and expanding at pretty much the same rate I don't believe it's an advantage. If the floor bricks are laid loose the gaps between them are sufficient to allow for free expansion.

[RADG24]

The base is made up of an inch thick cast iron sheet I had with a 4-5 inch thick perlicrete layer on top of that, this will then sit on top of a fully cast iron workbench so I am not worried about any structural issues.

Thanks for the explanation on that, I think I will lay the dome over the bricks in that case, as it seems much easier and if there is no great issue of differing rates of expansion then I see no real drawbacks.