Late reply but from Selden, a code sail sheeve can be .8 meters above combibox.
Agreed, the combi box is a cheap set up. Never liked sliding the halyard over the forestay when hoisting.
Selden advised on Sheeve. Also installed a 2:1
test run this week. I was running the code off the anchor stem but gusts would bend it slightly upward. I concluded that not a good thing.