Ergonomics of Wood Engraving

I often engrave on a block during an eight, ten or sometimes twelve hour day, with breaks for lunch and dinner. A few years ago I began to experience back and neck pains and figured it had something to do with the way I was sitting at the work bench. I realized my back was straining as I leaned over the block to engrave and I remembered seeing an unusual chair at Simon Brett's studio in Marlborough, England. He told me then that it helped his back and I figured this might eliminate my back ache as well, so I bought one at a local office supply store.
When I sat in the "kneeling" chair with my butt on the upper pad and knees on the lower pad, and my back straight, my work bench was too low. I could see that I had to raise the work surface to keep my back straight. Old phone books and piled up sand bags weren't secure enough.