The top is secured with 3 factory style turnbuckles in widow area and one in the area directly behind main doors
The rear door fabric section can be removed but not easily. Fabric is secured to door section with bolts which can be seen in previous picture. Then frame needs to be unbolted from lower door with 4 bolts. And finally upper door hinge bolts need to be removed. Not a quick job and I never plan to run without. Driving down freeway with sides rolled up there is no flapping or movement on the rear door fabric which I'm not sure you could do with roll up window?
The drawer system was my own design to best utilise all the space in the rear without seating back there. Plywood glued and screwed, covered with carpet, mdf drawer fronts and bolted down using factory holes from seating and seat belts. Wheel wells also covered with carpeted ply and bolted down to existing factory holes so whole area is one even level