We have only one jib (a 100%) on our J/Boat. The variation in the jib tension might be 3" or so from very tight to light a bit off the wind. While we have about 73' of vertical draft on the mast, I would think Niel's boat would have a good 2" or so of variation.
If he's always using a chute when off the wind, then I think the tension is a very different thing.
If your sails are cut very flat (like some racing sails on SOME boats), then I think the variation would be somewhat less.