If you look in the Important links Sticky you will find this:
They're pretty similar creases, so I'd imagine the biggest issue will be the felt trying to fold back into the crease it has "remembered." I would pop it back open crown. I don't know about everyone else, but when I do the diamond crease, I start with the open crown hat, and first do the center dent. From there I look down at the hat from the top and find the right point for the side points on the diamond, and push those down. Then I look at the back of the hat to make sure the sides are even and adjust the rear point for the desired amount of rake.
If the felt is not acting the way you want it to, it may be useful to mist the crown with distilled water from a spray bottle.
'''Greed: It ain't goin anywhere,' they should have that across a big billboard in Times Square!"
In my experience, turning a round hat into something with kind of square corners is difficult. I had to wet my Resistol twice before it took a decent diamond bash. If you keep at it, it will eventually stay.
The hat was too short for the diamond bash, so it went to a Boss of the Plains style.
Groucho Marx said it best:
“Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying all the wrong remedies.”