Totally agree with the guys. Sanding the back is totally cool. I haven't backed any of my board bows yet, and only one has checked. It's hard for me to hide the beauty of a bow with paper backing. That includes the ever-stinky oak. Start with 220 and get her smooth. Like Pat mentioned, make sure your corners are rounded. Not like 1/16", but a good 1/8 - 1/4" radius. With a great straight grained oak board, you're going to have A LOT of runoffs, but the good kind. A good rounding will help ensure you won't be hearing any "pops".
Good luck, and enjoy the results.