Just so we are clear I did this in the fall. But I figured I would show this off. I cannot locate the thread that told me how to do this, nor the youtube video but I'm sure someone out there can find it with a little effort. I DID locate a how to video but it's not in english. I posted it here because I think most of you capable individuals can catch the idea just by watching even if you can't understand what he is saying:
https://www.youtube.com/watch?v=UlHSdLJptkY

Now with that out of the way I can sum that video up in a few bullet points.

-remove the gauge cluster. on the firebolts, it is necessary to at least partially remove the front fairing. They reccommend removing it entirely but I did it without and just had it hanging awkwardly loose on the bike while I accessed the nuts holding the gauge pack onto the steering head. This process is ten times easier with a Lightning, but I have a firebolt so alas....

-with the gauge cluster off the bike you have to disassemble it and remove the "egg carton" on the right side that has the colored warning lights. You will be using a dremel or some other creative means to carve out a "basket" to hold your digital voltmeter. I used the really small ones on amazon. I got a five pack for like 10 dollars. THE QUALITY OF THESE VOLTMETERS SHOWS IN THE CRAPPY SOLDERING THEY DID TO THE WIRE PIGTAIL, SO HANDLE THEM CAREFULLY! (I ruined the first 2 I handled)

-link to the voltmeter I used. I really wanted to use the blue one on my bike but I destroyed it so I used the green instead. There's no way to tell what color they are unless you hook them to a 12v source so touch the pigtails to your motorcycle battery before installing to see what color it is!!!! https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 NOTE: you want the gauge to be the 0.36" size. They are actually smaller than you'd think, but they fit perfectly.

-Once you carve out a basket inside that egg carton that fits the gauge, run the wires through to the back and solder it in to 12V, or you can route them externally. I drilled a hole in the back of the gauge pack housing and ran 12V ground from the headlight ground, and 12V hot from the low beam since I couldn't find another keyed 12V source unfortunately. If you can find a keyed 12V on the back of the circuitboard and solder it in it will give an even cleaner look.

-reassemble everything and test out the gauge

Video of my gauge.

https://www.youtube.com/watch?v=tb8yixQ7XQQ

6 months later and it still works great. Something to notice is since the gauge isn't ran direct to battery, the voltage indicated MAY be off by 0.1 or 0.2, but it's not really that important for what we usually use a voltage gauge for (catastrophic failure of electrical components)

Please leave your ideas here and spread the video around to all your buell friends, I think this is a high priority upgrade to our bikes and looks OEM!