2 questions, really, resulting from my readings of the Patrick O'Brian historical novels, in which he often described a small square-rigged frigate running solely under close-reefed top gallent sails.

1. Did the force on these sails receive any amplification due to their high position on the mast? I.E., is there any leverage affect that helped propel the ship forward?

2. Assuming this isn't a factor, why would this be a common sail configuration? There is more risk for the top men setting these sails... Is it because the wind is more constant at these heights, making for easier sailing? Are there other advantages?

Thanks....