Rock stable now
The screen buffer uses 506.25KB of HUB RAM which is 1/2 screen, so it is duplicated.
(see post 21-22 Nov 2018 below)
The visible portion is smaller than 1920x1080 (1440x540) as currently there isn't enough time to setup the full width pixels, nor enough hub ram for the full pixel display. These can all be worked on as we are not at the silicon limits.
FWIW I have just reduced the visible pixels and increased the front & back porches. This is not the right way to do it.
After some time, the P2 is somewhat hot to the touch - no fan, no heatsink, ambiant ~25C
(jmg: please don't ask for temperature, fans, heatsinks, etc)