If you are using a small crane to lift, use a farmtruck tire and rim to lift the whole thing an inch or 2, then remove the bottom ring. (For suggestions on breaking the bottom ring away from concrete, see the article.) Then lower the whole bin, minus the bottom ring which you have just removed. The farm truck rim and tire are placed inside the bin and raised to the roof, centered on the collar to support even and centered lifting. (See pics of such a lifting ring in the article.) Then lower the bin, again and again removing rings. If you really want to remove the top ring and roof first and then use ladders to disassemble the rest of the bin, please let me take photos so I can create an article titled "How to Take a Vacation With Injuries." Your idea of concrete a few inches higher on the inside is great, but pricey. Brock brand tar pad works great and is much less expensive in labor and materials.