Dynamic shadows from the lantern MOD

[Bucic]

I've polished the mod. My main complaint was the flickering and jagged edges so I started sniffing. When I set the spotlight FOV to some small value like 30 degrees the shadows became perfect! From my test it all gets messy after 90 degrees and gets worse above this value, at least proportionally. Not only the shadows get worse. Additional graphical artifacts involving shadows appear.

Additional notes:
The further the lightened object from the lantern, the worse the shadow looks like. Opposite to what I was thinking before ('the further the wall the shadow is casted on, the more jagged the shadow').

This is why I'm going to prepare few versions of the mod so even those without the ModelEditor may test various variants and choose the balance between lantern light FOV and shadow quality that suits them.

My question is - is there some sort of tweakable shadow rendering parameter I can fiddle with?
An additional question - is this normal that shadow quality gets worse the higher spotlight FOV or is it just an indication of poor state of the renderer?