Viewing stereo cubemaps in VR, real life size adjustments?

Hi all, for those of you who are familiar with cubemap renderings and vr, how do you guys adjusting the size so the objects in the rendering photos looks as if its a real life size environment?
i have been trying with 10800x900 and the environment seems much smaller than it should. should i be adjusting the size of the render and up the scale to, say, 21600x1800?
Thanks