The mod in the form that was shown in my YouTube video was very buggy (as in... the player model's head covered the entire screen sometimes), and sometimes even crashed the game.
That mod eventually turned into my
Zoomed In mod. Zoomed In is the closest to "first person" I was able to figure out how to implement in a stable form.
If you want to poke into this "first person RF:G" idea further, you may want to try messing with the parameters in misc.vpp\camera.xtbl as a starting point.