RE: 4.0 m2 sail with 400 mast (luff 376)
I have had a lot of experience with smaller sails and I have to say the biggest single difference to handling and performance was when smaller, softer masts became readily available.
Yes, it will definitly work much better on a 370. If this is a sail you use fairly regularly it is well worth it. From my point of view those special days when it is really windy don't come around often enough to waste the oppurtunities to really enjoy them to the max.