Basically true... more to center for going to weather, but as the wind increases perhaps a bit further out. In high wind, I would guess about half way to the hiking strap on the 16 main and 4 inches on the jib traveler to open the slot.
The basics on the main are also related to the hull flying. If you cannot keep the hull down without sheeting out... travel out a little and sheet tighter.
On a light wind day, I sometimes travel a little too. If there is not enough boat speed for the hulls to track straight and you sheet to center, you can cause the boat to "crab" sideways which slows the boat. This is the same on a unirig in most conditions (14 / 17 main only). Travel out a bit... centered causes the boat to crab.
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