Need some advice. I recently bought a new Titleist 915 FD fairway wood/13.5° loft, with the standard Diamana 80 gram whiteboard  stiff shaft.  However I played the 913 FD fairway wood with the standard stiff Diamana 82 g whiteboard shaft and absolutely nutted the ball 265+ yds off the tee.    The launch monitor (and my limited experience playing) says I hit the 915 series about 7 yards further however I tend to hit it much further off-line versus my 913. It also feels lighter and I get quick with it and can top it.  I thought about putting the 913 82 g shaft on the new 915 clubhead and seeing if that would help. Is there anything "wrong" with this?  I'm sure the new 80g whiteboard is engineered to be "paired" with the 915 club head but I'm hoping to get straighter, longer shots by melding the two. Any insight?  Thanks!