Yep, it's possible, believe it or not.
Download: http://codeguys.rpc1.org/firmwares.html
1/ +R DL works
2/ -R speeds are still limited to 4x! (51S hardware not capable of 8x -R)
3/ Improved write quality
4/ Instant +RW bitsetting feature
Discussion & more info: http://club.cdfreaks.com/showthread.php?t=100956
+R DL burn #1:
+R DL burn #2: