Use CRU, it definitely works
I have an Asus MG279Q, stock FS range 35-90Hz, as it's 144Hz panel I went 57-144Hz FS range
i) Download CRU.
ii) Click edit across the top.
iii) Make sure "Range Limits" is ticked.
iv) Change the freesync limits to what you want.
v) Restart the driver with restart.exe or restart64.exe.
Even with that range LFC will work as max refresh is ≥2.5X min. refresh.
How I verified mod had worked was running game with overlay showing FPS (ie FRAPS, etc) and then compared that with the Hz shown in OSD of monitor, as they matched at FPS changes, FS was working (plus no tearing, etc).
Once you have done the edit to FS range, mod will not be removed with reboot, the way to remove mod is using the reset-all.exe .