Seat foam?

I would think a small area is repairable if the rest of it is in very good condition. Overtime it seems the foam contracts / compresses and new covers my actually fit too loose over it, JMO.
Ahh, I didn't even think of that. Back in the day I just go to the Boneyard or go buy some from somebody that we're still in good shape. So I've never actually gone through this part of a build. How would you repair it just spray from it let it dry and shave it back or do you have to take and square out a piece of some type of high-density foam and then try to glue it in there then shape it back?