The pro tongue liner stiffens the boot up a lot. Like a significant amount. I have the all white first chair 10s and run them with the wrap intuitions with a 12 flex tongue and it feels good. But then I upgraded to the pro tongue and had to switch back to the 10 flex because it was almost too stiff.
The first chair 100s don’t come with the pro tongue just the normal tongue. I would recommend moving up to the 120 or 130 that have the pro tongue. Completely changes the feel of the boots.