Glenn:

I count 8 to 1 with the cascading system. What am I missing?

I see a 4 to 1 outside the boom and a doubler inside the boom. I do not think that the sheet coming out of the boom to the bottom block adds any purchase as there will be no more line comimg out of the bottom block than pulls on the doubler block inside the boom.

I hope your boom is stronger than mine, small Tiger round boom, as it looks like too much of a compression load. If you are putting that much in compression it will be ready for any side force to bend or break.

Later,
Dan