Of course, I don't know your individual situation, but I hit the ball fat when I decelerate. I get too intent on what is about to happen at the bottom of the down swing, and I wind up decelerating my hand swing. I can get around it by focusing more in accelerating my hand swing and paying less attention to where the club head is. The club will straighten itself out. I don't need to help it by decelerating.
Some people seem to think they need to help the club "whip" by slowing down at the bottom of the down swing. At least, I used to think that.
Perhaps you could try not focusing on where the club head is going to hit the ground and let your hands swing all the way around. Focus on good body rotation, weight shift, acceleration, etc. Don't focus on the ball or on the ground. Focusing on a spot on the ground might be causing you to decelerate.
I still hit fat sometimes, but so do the pros. I saw several fat shots in the Tour Championship yesterday.
As per the specs on XR irons, the stock shaft lengths are:
6i = 37.875"
PW = 35.75"
AW = 35.50"
SW = 35.25"
So, your 6I + 1" now is 38.875" long.
If you have already extended these two wedges 1" also, then you would extend their shaft length by 2".
If you have not already extended your wedges, you would be increasing the shaft length by 3".
A couple of things to consider:
Shaft length + loft helps determine how far a given golf club will launch the ball. If you make the wedge shafts 2 to 3 inches longer, you likely will get yardage compression. You might get a PW that flies longer than your 9i.
Safety factors: The clubsmiths at GolfWorks do not recommend extending non-putter shafts beyond 1". You run the risk of creating shear points, with club possibly coming apart.
If you like longer shafts in the short clubs, try the single-length irons.