Use of insulating bricks in batch box

Hi All;
Building two batch box's this spring.
I can buy as many brand new insulating firebricks @ $1 each as I want/ need.
My intent is to use them as the octagonal riser base then set my five minute riser on top.

Next i'm thinking of the box itself.  Other than the sloping brick at the bottom. I don't see much cause for abrasion of the walls or roof?

My question,  can I use insulating bricks on the walls and roof?  And use the heavy firebrick just on the sloped bottom?

I'll be using these bricks ) Brand new  Skamol Molar Supra insulating fire bricks, good for continuous duty at 1742 F

I received a reply from Peter over at donkeys forum.
Do not use the soft brick on the walls.  apparently there is still to much abrasion there.
Insulated brick for the roof is fine.

Thank You Peter!

Thomas, I didn't realize you meant the pink type, those are quite good. I've used those in the past at Paul Wheaton's and those are soft but relatively firm. Given the fact you being the only user would be a workable situation. When you are aware of the limitations of the material, please use it and stay careful. As a material for a firebox from a pyro point of view, those Skamol bricks couldn't be any better.