Was having a conversation about this with fellow F18 / Tornado Sailor about an hour ago.
We initially put ours at shoulder hight, whilst my mate (who crews for Macca) has his at head hight initially believing he should be pulling down.
At the end of each pull our hands are finishing off behind us and at hip level which means we are not pulling through the cleat. If there is a little gust or the halyard slips in our hands, you loose a little of your hoist. You must also pull up on the final pull to cleat off.
We have now come to the conclusion that we should have them set at hip level measured whilst standing on the tramp and allowing for a little sag. This way each pull is pulling through the jaws of the cleat eliminating the slip in the halyard whilst hoisting. I will be making the change as soon as we get up to Yeppoon for the Worlds.