For any and every 11-cell pattern/shape, there are 39,916,800 possible combinations that an attacker could face just within that one pattern - e.g. A1 to A11, and 258,520,167,388,849,766,400 combinations if you use 23 cells. The checksum is calculated post hoc and pursuant to the 11-cells selected, and there are an additional 128 possible checksums for every 11-cell combination.

I haven't run all the numbers for the total number of possible 11-cell patterns but it is an extremely - extremely - large number. You would be far better off applying that energy to mining bitcoin directly.