My solution for AV modding an original Famicom was to use the PCB sold at console5 by Cathouse games. I modeled a small tray that connects to the screw post and a grommet with a wider diameter. Rather than drill three holes in my Famicom for the AV ports, I ran a pigtail out of the larger back grommet. I purchased the pigtail 3.5mm female jack on Amazon.
Check out the PCB here at Console5.
Kit includes my tray and grommet. Famicom and The Cathouse games PCB are not included.