Dave,

If you are using a furler, chances are you will not be able to adjust your luff out on the water. If your rig is not tight you will likely see a nice bow in the forestay. This is what will hurt some of your ability to point... among other things... (a tight, flat main etc...).

If you are not using a furler you will not have to rig as tight since you can have the ability to adjust the jib luff from the tramp. Even then if the rig is too loose you will still have the bow in the forestay regardless of how tight you pull on the luff downhaul (this is in moderate to heavy air of course). Have someone snap some pics of your boat from the front while you are sailing and you will see this.

A lot of guys I know have pins and or quick release on the side stays so they can loosen them for heading downwind over some distance.

I always set my rig according to conditions and pretty much leave it alone until the race is over. Unless conditions change drastically. Then I will tighten or loosen accordingly. Remember. There are quite a few things that are different on an EX. Some do not apply to stock NA's.

AJ
Nacra 6.0 EX w/spin