I really like how my twin famicom controllers look so I decided to mod them to fix things that bother me. I performed the following mods:
1: Relocated the cord so it comes out a hole in the top of the case instead of the side
2: Wired the controller into a nes controller port
3: Modded the pcb so it can work with extension cords
After wiring up this pad I quickly discovered that it wouldn't work with extension cords. I probed my extension cord it's wired right so I took an educated guess that too much distance messes up the control pad signals. It's safe to assume this considering this controller is meant to be hardwired into a famicom without extension cords. My dogbone nes controllers which I've used for years work fine with as many extension cords as I like in between the control pad and the system. I decided to compare the dogbone pcb to the pcb found in all hard wired famicom controllers / original rectangular nes controller. The big difference I discovered is in the dogbone controller there's two 3.6k ohm resistors connected to vcc and the other ends connect to cup and out 0. I added 3.6k ohms of resistance on my twin famicom controller pcb between these two spots and sure enough that fixed the controller cord length issue.
Here's what my twin famicom pad looks like:
Here's a quick schematic of the mod: