The next step is to add some foam inside the helmet. The easiest way to glue it in place is to use some glue spray.
First, I use some 220 grit to lightly sand the inside of the helmet, then measure the inside with a piece of paper that's used as a template to cut out the foam. Once cut out and test fitted, I spray the inside of the helmet and then one side of the foam.
After pressing the foam inside the helmet for a few minutes, I test fit the visor and check the reference photos to make sure it's in the right spot.
With that done, I mark inside the helmet with a pencil where the visor should go:

I cut some narrow pieces of foam that will act as a brow that should go just behind the visor. These are placed just behind the two lines using more glue spray. Once the glue sets, I apply contact cement to the edge of the visor and then place it behind the brow pieces:

First, I use some 220 grit to lightly sand the inside of the helmet, then measure the inside with a piece of paper that's used as a template to cut out the foam. Once cut out and test fitted, I spray the inside of the helmet and then one side of the foam.
After pressing the foam inside the helmet for a few minutes, I test fit the visor and check the reference photos to make sure it's in the right spot.
With that done, I mark inside the helmet with a pencil where the visor should go:

I cut some narrow pieces of foam that will act as a brow that should go just behind the visor. These are placed just behind the two lines using more glue spray. Once the glue sets, I apply contact cement to the edge of the visor and then place it behind the brow pieces:
