I've installed the CS 757 on P3DV5.  When I installed my another company aircraft i had to modify to registry so that if P3dv4 would go to P3DV5.  Theirs a Youtube video on how to change registry so you can install another company to V5.  Change the registry at your own risk.  The  757 does work but it can crash very easily.  Do not select any 2d displays including the fmc.  MOST IMPORTANT do not select any autopilot cancellation warning or autothtottle cancellation those black switches next to the backup attitude and altimeter it will CRASH.  Try avoid using the zoom mouse function.  Avoid pushing mic or any clock buttons on the cockpit .  I do not know exaclty but the 757 will crash about 3/4 or 1 duration of the flight.  It maybe a command or the sim itself.  I'm using Active Sky P3d Beta, GSX, Ezdok.  Please adjust your sound INI file volume controls and make sure to install the sound fix in the forums for full sound functionality.  The ACE utility and liveries work flawless.  For some reason the sim will crash on the very first flight.  Please try a second attempt.  Still looking into the issue.  Make sure to turn off dynmaic lighting it seems to eat up a ton of frame rates.  Some loss of frame rates with vatsim.  I'm running a older version of nvidia display drivers some fps issues with another company, that may slow 757 down as well. Hopefully captainsim can get in update on the 757.