Manually set frusta (stereo vision)

I am attempting to mod the frusta settings of Xonotic.

Two things:

1. Is the source/cl_screen.c file what I need to edit

2. Will editing frusta affect the rest of the game code?

Can you explain what you mean by frustum with respect to stereoscopy?

Does it have anything to do with the field of view (cvar 'fov' ?)