I installed the trial of Viewpoint version 3 today. The manual states: Image sizes up to 200 MPixel (JPG, TIF, 8 or 16 bit) can be handled.
It works fine with sizes of about 20 MPixel. If the viewpoint correction produces none rectangular images, the image size increases. Not used parts of the area is black (No autocrop selected). That is what I want.
At a larger image size (I could not find a threshold) this behaivour changes and the program/plugin reduces the size of the resulting image. For example from 100 MPixel to 30 MPixel. The input and output files should be far away from the 200 MPixel limit.
As many images I want to use VP for are very large panarama images, I need larger output files.
I am using VP 3 as a plugin in Photoshop cc.