I used the gray minicell to make a custom bulkhead in my Super EZ, cutting and layering the foam into a wedge to create the most pressure on the heels and middle of my feet, with only light pressure on the balls of my feet. After 1 season of use, the 3 layers of 2-3" each compressed by a total of about 1-2", so now I am going to reconfigure the design over the winter.
In my boat, I am able to exert considerable pressure on my bulkhead with the use of a ratcheting backband. I probably need to outfit my thigh braces better, but as I ratchet down a lot of the pressure goes right into the bulkhead, thus causing the compression over the season.
I didn't use glue, but I did use duct tape to hold the layers together. Then I jammed the wedge into the front of the boat with friction holding it in place. I have also used foam blocks in a bulkhead many times on a boat my wife used to borrow from a friend. They never came out, and she swam quite a few times. I would advise against using glue - just cut the foam a little big and jam it in.