Hello Aaron, You can find the modification video on YouTube. As far as I remember, it's a simple mod that adds just one extra wire from the H7 side. However, with my limited experience, it will tax the battery/alternator and also can burn the reflector in the long run. It's better to go with something like the Osram Nightbreakers or any reputed 200% advertised brand X. Yes, the life will be pretty short, but the luminosity is far better. The second option is a good-quality 4000k to 4300k 60W LED.
Welcome new members!
I also use to make a universal headlight mod that would work on any bike that had to dual headlight problem which was not just the FZ6.
The issue as mentioned was overheating the H4 dual filament lamp when the high beam filament was activated. The low beam filament should be switched off when the high beam filament is activated. The H4 was designed to run only one filament at a time.
The fared version of the FZ6 did not use the low beam of the H4 and only used the H4 for it's high beam filament. The harness and switching does provide the switching but it is terminated in a harness plug below the battery. You can make your own wire with the proper pin and insert it in that harness plug running the other end of the wire to the low beam connector on the H4 which would provide the properly switched power. There are 2 other ways to skin this cat but since I don't make the universal kit anymore and the other way is a youtube hack where you tap into the handle bar harness which is probably the fastest way but most invasive. The best ways are a little more work but less invasive and neater.