Roger is spot on.
We have Overdrives from 10 down to 5.5and a 4.6 CR and they will always load up the last 2 sheaves.
I think the extreme downhaul on these sails make it difficult for all the sheaves to share the load evenly.Dont get me wrong we think Overdrives are a great sail ,and the CR as well but they need serious downhaul.(Dont all cammed sails?)
We use a crank type downhaul for these sails,overtension,then back off 10mm till the pulleys sit almost parallel to the extension.This would not be possible without a crank type downhaul tool.