There are multiple trains of thought for the height of the primary drain. Some like to use no pipe at all and just put a strainer directly into the bulkhead. This usually keeps the overflow box cleaner because it stops sediment from building up on the bottom of the overflow.
Others like to add a stand pipe to decrease the amount of water that will drain into the sump when the return pump is turned on.
Ultimately it is your decision. I prefer no stand pipe because I have been shocked by how much crud can collect in the bottom of an overflow. Just make sure your sump can handle the extra water volume when the return pump turns off.