Here you go (http://www.raphnet.net/electronique/nes_mod/nes_mod_en.php), nice one on the stereo mod.
I had spoken with the individual responsible for these modifications a couple of months ago, commended him on a job well done and brought to his attention the NES RGB information from the post's here at NFG.
He said he had been looking for NES RGB information/inspiration and was excited that I had pointed him in this direction. I have not been in contact with him since and do not know if he has completed the NES RGB modification.
The NES stereo modification is top notch stuff! I have done this to one of my NES consoles, but instead of wiring up new audio outputs I disabled the RF output and used its preexisting RCA type plug for the second channel of audio.