There are several threads on the "cross flashing" - check at the top for the "unofficial firmware" page - it has ALL the stuff, and the posts have lots of hints and tips, so read through it.
I'm still waiting to do it myself. I want a full clear path to warranty coverage in the meantime, and since G7P9 let's me run BenQ's QScan (which the older one's don't), and since "T" hasn't quite received an "all clear" from the majority of members here, the "P" seems to be quite good on balance.
Still, there's something about being most current that's attractive; I'll get to it soon. I downloaded nearly everything on the "unofficial" page - a great resource!