I used to own a BenQ W1080ST. I controlled the projector using RS-232 in conjunction with my Philips Pronto Professional TSU9600 remote. I did learn the IR codes from the OEM remote though.
And yes, I also had to send the "Power Off" command twice. Looking at my macros that involved powering off the projector now. I sent the "Power Off" command followed by a .25 second delay action, then sent the "Power Off" command again. Never had any issues. The URC MX-900 can be programmed is the same fashion. URC's CCP software offers a "DELAY" action as well.
LP Related Links: View my profile to access various links to key posts and downloads.