superman

I have a 60" screen, and for certain older shows recorded in SD it would be great if we could reduce the size of the picture down to say 50". Does anyone know how this could be possible either through TV config or existing apps? The closest I can find is the built-in functionality for 'multi view' but this gives a very small 30" display with no apparent way to increase the size. Is it possible to re-use the code used in 'multi view' and adjust the configs slightly?