William Bronson wrote:
I find no insulative bricks locally, and the dense firebricks are expensive,so I am planning to cast slabs of perlite/rapidcast/rockwool fibers , for the fire box.
You might want to re-think the cast slabs mentioned above. Rapidcast will not live long in the environment of the burn chamber. Look for refractory cement instead, it comes in premixed tubs or in powder form. Rapidcast is Calcium Aluminate and is only good to about 900F, after that the water in the crystalline structure begins to break down and evaporate and the structure will flake apart. Refractory cement has enough Calcium Aluminate to set hard at room temperature and the primary binders begin to fuse at temps above 1000F and are good to somewhere higher than 2400F. 1400F to 1600F is the standard temps inside a rocket stove burn chamber. Refractory cement is somewhat more expensive but your project will last many years instead of a few months.