Everything tou need to convert your Philips to a BenQ 1620 Pro is at : The Unofficial Benq firmwarepage
You need to download
The latest Firmware for Benq 1620 (B7T9) cvt and
The Benq/Phlips firmware flasher
Unpack both and put in the same dir, launch WinDWFlash.exe and select the cvt file in the same dir. Start flashing now.
It's really that easy !! Going back is the same thing, you need the CVT file for the Philips.
BTW : I also bought the same Philips drive and converted it to the Benq 1620 Pro and never bothered to go back !! IMHO, Benq fw is just better !!
(If you'd need to go back, I have all the files needed).