In 15 kts you should not have the outhall tight.

The only time you want the outhall tight is once the downhall is on absolute maximum when it's much more than 15kts.

If you set up the outhaul to have the bottom of the sail just snug when the main and cunnigham are on hard, then as you relax them (lighter air) you will find that the foot of the sail will loosen automaticall and give you a little draft.

Some rather competitive F18 sailors just set and forget the outhaul. The Infusion outhaul does not appear to be designed for adjustment while racing (it is a line from the back of the boom through the ring on the clew of the main, back to a slot at the back of the boom where you jam a stopper knot on the line).

So I suggest that once you get outhaul in the ballpark it is not a control to bother messing with (on F18 class boats)

Chris.