[Req] Shift Two-Point-Perspective by a certain amount?

[numerobis]

I'm working with the Maxwell plugin for SU and since it isn't possible to show the result of an image shift directy in the viewport, i was wondering, if it would be possible to at least achieve this by a separate plugin, where you can specify the camera shift by a numeric value based on the percentage of the total image height? (as it is in Maxwell)