It's also going to change with the surface. Some of the courses we run on are fairly slick, and/or rough. This is going to call for a different tire pressure than when we are at the high grip events. Track temp makes a difference too. I'd say to start, use the shoe polish trick on your tires to see what you need to do.
If anyone does not know, you put 3 shoe polish dots on your tires, trying to get the center to be right at the edge of the shoulder. There will be a little arrow pointing towards the tread on the shoulder, and the tip of the arrow is where you should center it.