Well, GP3 were designed for 4:3 video screens resolutions... By the way, I can run it in 1280x1024 (which is a 5:4 resolution), try a recalibration, it may find your resolution, no?
GPGSL-3: Fox race driver and team manager - 2011-2012 Constructor Champion - 2012 Driver Champion
Season 9 - #18 Erick Von Draxeler - #35 Marcus Bongardt