rather schematic, but the box is just 4sides paneled with wooden beams in the corner over the full length and hDPE on top....2m high or 6ft (+-) is sufficient i guess, if you can go bigger, by all means do, as you see, im planning on getting my gardenshed pimped
Sorry for triple posting, but just for info, the sudden transfer is solved by just adding about one wheelbarrow of dirt to the bottom, its both stabilizing as smoothening
i looked through the 'post a picture of your drop in' thread and found one that was basically this exact design. So i took that design and made a drop in but with my own dimensions, so it's a pretty flexible design and really easy to make too. all i need to do is add ply wood to the top.