Has anyone successfully used g-sync with P3D or have any opinions on whether or not it should/could work with P3D's windowed fullscreen mode?  Anyone using g-sync for FSX or XPX?

Try the latest NVidia drivers 353.06 read info below;

GeForce Game Ready Driver
" In addition, this new Game Ready driver provides a number of new gaming features and benefits based around G-SYNC technology, Dynamic Super Resolution, and enhancements for the latest new titles."

 

Gaming Technology
Supports G-SYNC technology in windowed mode, offers both G-SYNC (V-SYNC on) and G-SYNC (V-SYNC off) options, support for Ultra-Low Motion Blur (ULMB) in the NVIDIA Control Panel, provides Dynamic Super Resolution (DSR) for notebooks with discrete GeForce GPUs, and optimizations and bug fixes which can provide increased performance for Kepler-based GPUs.