I really have no idea, but I assume I can stitch seamless, if I render with overlapping GI.
My current thinking is, if I have a 60 degree horizontal FOV, and I need to create render tiles....
60 degrees horizontal / 5 = 12 degrees, so I would set the horizontal FOV to 12 degrees, then rotate in 12 degree increments left and right. That should allow me to stitch together one row of images seamlessly and look like the original 60 degree render?
Never tried it, but is it logical? I hope so.
But how much VERTICAL degrees do I get with a horizontal FOV of 12? I have no idea. Can anyone say?
PS: If this is impossible or too difficult, my virtual "Me" would spit out a curse and simply go buy the Deep Edition, just for being able to render large!!!