I got TwinView working today, love it

. However, when I start a game (like Max Payne 2, in windowed mode), a third of it is on the right monitor and 2/3 is on the left, or some other odd condition (like having half on each side and a bit off the bottom of the screen). I'd like it to take up the entire left screen only and leave the right screen free, but it doesn't want to do this. I've tried editing settings within the games, and I've looked through the nVidia readme and changed some MetaModes, but it didn't help. Can anyone help?
PS: I'm running Fluxbox 0.9.10 with 1280x1024 on both monitors.