The OFX plugin Reframe360 actually worked, thanks, but I was never able to achieve less than 2X zoom while still filling the frame. Maybe I was doing something wrong. I wanted around 1.1X dynamic zoom max, just to make the video more interesting. I am capturing live action with just one stereo camera, so dynamic zoom would help. The issue with zooming more than about 10% is the resulting 2880x2880 image becomes too blurry when projected in a 120 degree FOV headset.
I also tried projecting the R/L images onto 3D spheres and moving the camera, but those were too blurry no matter the zoom level. Apparently I don't know how to do that right. I am going to need a tutorial of some kind to make this work. Until then my viewers will just have to do without. I have spent days on this...