The problem with planks in one pic...

So the Commandant just approved planks as an alternative to crunches for the PFT?

The pic above illustrates the problem with that.  Notice the Marine at the far right (as you're looking at the pic)?

He's the only one doing it right.  The one in the middle and far left should be no go's.  Raising your ass in the air takes the strain off your hip flexors (I think) as is a common "cheat".

Haven't read the details but this thing is gonna be problematic...JUST MARK MY WORDS!

Change for change sake is always bad.  The PFT has to evolve...I understand that, but this ain't a change for the good.  Modifications to the crunch had already taken place to make them safer. 

Teach the exercise so that its done correctly.  That's how you improve things.