The stiffer shaft will reduce spin rate and increase contol.  If your old ball flight didn't balloon and it's the optimum flight, then you will lose distance.

I would head to the nearest launch monitor and bending fixture and test for spin rates.  As a general rule you want 1000rpm for every iron.  So, a 6 iron should spin around 6,000 rpm.  Give or take 2-300rpm for draws and fades.

You should start with the 6 and work your way down to the lowest playable iron.  You can bend lofts stronger up to 2 degrees or so to make the most difference.  Then head back to the 7 iron and start really dialing in your gaps.  You may find the need for one less longer iron and one more gap wedge.

And as another general rule we use at the studio here, shafts contribute roughly 20% of ball performance, while the clubface contributes 80%.  Find the right clubface and the shaft comes along for the ride!

RC

I put my AP2's together last fall with hard-stepped Aldila MLTI stiff 105 gram shafts.  I've been playing Titleist irons since the 962's.  I've noticed I have difficulty controlling the flight of my short irons this spring.  I have a loft-and-lie bending machine and have been doing my own club work for many years.  I played in college and played serious golf when I was younger.  This is the first time I've had difficulty in flighting my short irons.  I have sets of 704's and 962's set up the same as my AP2's, but don't get the ballooning.  I really like the AP2 head and love the feel of the club.  I have no problem moving the ball left or right, but up or down, .......

Thomas:  how are the lofts configured?  It would be easy to make them stronger in the short irons.  Maybe add an extra gap wedge.