Design questions for a rocket heated hot frame

I'm planning to use an outdoor rocket to heat a batch of frames. They will be built on a concrete patio, with double walls of stabilized earth brick, with perlite insulation between the walls, glass or polycarbonate lids hinged to a wooden frame on top of the brick walls, and a mass of subsoil packed around the rocket stove pipe as thermal mass, with the plants siting on top of that.

I have a few questions;

1. How best to insulate the frame, especially underneath? Will the perlite in the wall cavity work? Would something else work better?

2. How to manage drainage? I don't want the earth mass to turn into a soggy mess, and I especially don't want to soak the insulation layers. Also, even though the bricks will be stabilized, I don't want them to get soaked. (I will be using stainless steel or aluminum stove pipe to avoid corrosion, and I will be treating the walls with sodium silicate (water glass) as an added protection.) How to drain off the water before it soaks into the mass? A ferrocement slab with a shower type drain?

3. Will I have to take special steps to get a Rocket stove primed in outdoor conditions? (The core will be under a porch roof.)

I'm starting to think about a cement/ perlite mixture; still don't know if this will work.