Hopefully you haven't been given row 3.
I now pick row 4 because if there is no one next to me in row 4, I can raise the arm rest and have quite a wide berth.
Row 3 has the rigid arm rest so you can't raise it, you can stretch your legs forward, but not across even if no one is next to you.
Granted on that DPS flight, it might be that there is/are empty seats next you to.