ok, I read it again but your sentence is a bit confuse at first sight.
Yes, you can do an egg with that foam
problem will be some overshaping because have plenty of meat for a 164 guy
also, you ll find that after you shape the tail rocker and add a kick to loose more the board, you still have too much foam on that place so the only option is mowing from the deck. In lamination, add one 4oz patch under back foot.
I was going to use that blank for a 6’-0" x 21" wide White Diamond type board. You could also make a simmons type board out of that too, there’s plenty of foam in there. If I was going to make an egg out of that I’d cut a few inches off the nose and tail. I think there’s way too much rocker in there as it is if you go 6-5.