Very interesting thread... Though I think you could load up more weight if the grain of the wood was going the other way. Though all other test will be done in the same direction... My guess is your going to see a lot of them fail only because the wood let go first and not giving an accurate Shear load test for each glue. Perhaps using the block of aluminium would have been a true test of the glue, and not the wood..

Very good non the less and thanks for taking the time to do this.