One thing not mentioned here, that could help: I still use an old Radio-Schack desk, metal and thick plywood, which has its front edge lowered 1 inch. I mean, the surface bends down in a smooth angle , so you place your arms on a slope and not on the horizontal surface. For more cushioning, I lye a tablecloth folded in eight over my working area. My desk resembles an italian restaurant, but it is very comfortable.

Un abrazo - Andrés