I have a few ideas on that:
1) When you lift the board, especially when it's fully down, you're not only pulling the board up, but also pivoting it back. Since the line is vertical (or nearly so), you lose efficiency due to the force vectors involved between the line, gravity, and the CB pin opposing some of your pull.
2) There could be excessive friction somewhere in the system. Was Jim measuring the force needed to lift the board, or to hold it static at some height? In a frictionless system those two should match. As friction increases the force needed to hold the board static will decrease, and the force needed to lift it will increase.
3) Are we sure Jim's rigging matches the diagram? In particular, if someone rerigged the lower block 8 and actually used it as a block, with line 1 running through it, down to block 5, and back up to block 7, that would be quite bad. Block 5 would put half of the weight on each of the two legs of line 1 that go through it. Block 7 would be pulled all the way to the left, binding against blocks 8 and providing not mechanical advantage. So all you'd have is 2:1 from block 5, and lots of friction from blocks 7 and 8 binding.