Yes, you can do this. I did it with a 4+4. When you log in, the ticket quantity will show all the seats in your account, which will be 4. You'll have to change the ticket qty to 2, pick your first 2 seats, and then add them to your cart. After that, you can pick the other 2 seats in a different row. If you don't do it that way, it will force you to buy 4 consecutive seats.
If you can't get it to work, have your ticket rep's number ready and call them. By all accounts they are super helpful when they're needed.