I don't have FAH to worry about but I note you used xorg-edgers/ppa rather than the graphics-drivers/ppa you listed above.
Also, did you do that on a box with onboard graphics ?
I find that I need to uninstall the iGPU drivers and disable it and also add nomodeset to grub as follows...
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"
I usually do get it to work but it's a pain.
Have you noticed an increase in PPD for GPUGrid (or FAH) with that version ?
if i understand you ... you use the on board graphics chip for your display and the off board gpu to crunch ...
i cant live with that ... 10 seconds for a mouse click to respond ... nope .. dont got the patients for that
and i accomplish this by setting the BIOS to use off board Video ... so on board is "disabled" b4 i install the OS
i didnt use the drivers in the link because ...
i dont know how to install them ... so ... used what i could get running ... still ver 346.96
if someone wants to paste an "exactly" how to
use the link i posted ... im all ears
as far as performance ... im still messing with my builds ... so im not getting clean 24 hr runs ... before i downgraded to 346 ... i got a few days in a row of 2.2m PPD @ GPUGrid ... i did have the vast majority of one day of crunching yield 2.5m after the downgrade ... but ... im not going to say its an improvement until i have a few days of uninterrupted crunching and the PPD settle down into a decent average so i can judge