There is a way, but I don't recomend it... Turn off your computer during the render. Don't shut down, turn off the power. When you reboot, the partial file will be found and created by your OS. Now, re-open Bryce, make sure the sun is not linked to view (in either stage), and flip the camera 180 degrees so that your scene is upside down. Render to disk again and when the readout reaches the proper precentage, turn off the computer again. You can then splice the two images together in a photo program. This will not always have the desired result. Many times the hues will be slightly wrong at the split and will make an obvious line but AFAIK, this is the ONLY way to salvage a render to disk.