I just returned from a trip using an NSI golfbag. I've flow with it several other times but when the limit was 70 lbs.. I was nailed with an oversized bag charge only once on an interisland commuter out in Hawaii. With the new 50 lb. limit you
may be hard pressed to carry two boards and two kites in the same bag along with your other gear and accessories. I would try to preweigh things and distribute items among your second checked bag and carry on luggage. If you are traveling with someone else who may have spare space/weight, even better. I've carried two kites in vacuum bags in my carry on bags so a lot is possible. American now allows kiteboards subject to size and weight limitations. Not all airlines do this and the golf bag ruse isn't always that effective. They could have put some interior pockets in the NSI bag and perhaps made it just a bit shorter. It is noticeably longer than a real golf bag. More travel and packing ideas appear in:
http://fksa.org/showthread.php?t=1018 Have a good trip!