The official line from Cannondale is fork length measured from the bottom of the head tube to the centre line of the axle. This equates to the a2c measurement for the fork, plus the height of the lower headset cup.
Std frame – 530mm, MX frame 570mm
So with Pikes at 517mm a2c you have a spare 13mm for the lower headset cup on a standard frame. If you wanted to fit 150mm forks an integrated headset would allow this and not exceed the recommended max.
I really don’t think an extra 10mm of fork travel would matter, although the guy I saw the other day with a set of dual crown Nixons on his standard frame may have been pushing the limits a touch though..