Direct To Rift does not work currently with vorpX. You have to use extended mode. If the game does not hook for some reason, you could try to add “-32” (without the quotes) to the game’s launch options in Steam like suggested above. Definitely worth a try if the 64bit version doesn’t work.
Have The Rift as my Primary Monitor, in VorpX i have “Usw System Seeting”, in Steam i set the Launchparameter on -32 but the Game Starts in Full Size Mode and not in the Splitscreen….