I just bought/installed an FRX for the first time about a month or so ago. To avoid writing a super long post Ill sum it up with three lessons I learned. I originally installed on an old import LP custom that I've had for 2 decades and was probably 2 decades old when I got it. Of note, I am a true DIYer, I dont watch videos/read instructions unless there is something I cant figure out on my own so I learned these things through trial and error and when I couldn't get action where I wanted I finally watched a video... My FRX is now installed on an LTD sparrowhawk. While the FRX is meant as a nearly "universal" replacement TOM/STP guitars, here are some things to consider.
1. The FRX wants to be on a guitar with jumbo or xtra jumbo frets. While you can certainly mount it on anything with TOM/STP, by design there is only so much height adjustment possible, especially on a carved top guitar. Bigger frets buy a lot of leeway with the set up and getting action where you want it.
2. The FRX was designed to replace tune-o-matic/stop tail guitar bridges on gibson guitars. While the design is almost "universal" for TOM/STP guitars, there are differences in carve top geometry, tom/stp mounting, headstock angle etc. that must be accommodated for during set up. Watching the floyd rose video, I determined there was a reason they used an SG instead of a Les Paul...
3. You can set up the FRX in multiple ways (float/dive, angle of bridge to bridge plate etc.), you will need a very different set up position if you plan to also use a Dtuna with the FRX than if you dont...
In short, I wanted a les paul with a floyd so I got the FRX. After installing on an old ass import LP and not being happy, I moved it over to a LTD sparrowhawk and now I'd argue it is the most stable and easy to set up floyd I have. On a guitar with jumbo frets and a flat top I was able to achieve perfect action and playability. I've since added a dtuna and it turned a guitar I liked but wasnt inspired to play much into a guitar I really enjoy...