First off, I am the guy who mentioned the CMU is part of a building system. Your comment is true that the system approach is done to provide tensile strength but also to effect the twisting moment of the wall.

My concern would be the point load that you are applying to a brittle material. A common method of splitting blocks is with a guilloten (sic) that requires very little pressure (granted, it is used on the faces of the block). If the top of the block were capped with 1/4" thick steel plate, the point load concern disappears. Using a single layer of solid wood instead of a steel plate still presents the same issue...you would actually be better off with two layers of 3/4" plywood than a 2"x8".

This is why cribbing works so well for me. You have multiple layers of hardwood at 90 degrees angles to each other. Any one, two or five individual items can fail without a serious risk of the system endangering your life. To be double-sure I still place a steel plate on top of the cribbing but that is because I already have them. All of my cribbing material is off-cuts or salvage (mostly old hardwood flooring) cut to 18" lengths. The steel plate is left over from jacking up sagging floor joists in houses.

Onkel Udo