Oh, you’re right, I just got access to it, thanks for the tip!
On the other hand, however, in regards to the subject of this thread, I guess I was expecting something… easier!.. I don’t quite follow what exactly needs to be replaced with… I found both files in my computer (PlanarReflectionShaders.usf + PlanarReflectionShared.ush), but I can’t quite understand what needs to be changed in which one of the two files…?
In any case, I may be wrong, but the way I’m seeing the parameter “Prefilter Roughness” works, it is not going to achieve the effect we’re talking about just by adding a horizontal blur. Not only is Prefilter Roughness locked to a maximum of 0,04, which seems to be an extremely low value, the effect it creates also seems to be homogeneous, as in, it blurs the entire reflection as a whole, not having into consideration how far from the surface the reflected element is (I expected to see something like raytraced reflections…? As seen in this video - timestamped: https://youtu.be/tjf-1BxpR9c?t=273) 
Besides, lowering the other mentioned parameter “Screen Percentage” just seems to pixelate the reflections, taking image quality away
Is it possible to achieve the result seen in the video I linked? If so, how?
Thanks!