Building a password rig with 0 success... help needed!

[kcccs12]

Update to my post above with some numbers and info...

Installed Ubuntu 18.04.3 Server:

1. All defaults + openssh
   
2. Did a full update, installed gcc/make
   
3. Downloaded linux driver from Nvidia: link
   (Installer screamed about Nouveu, run the disable command, reboot, didn't work. Disabled Nouveu according to blackhills blog --> here. Then errors about X and 32bit libraries, but otherwise seemed to install correctly.)

First hashcat benchmark runs successful, one GPU installed:
Hashmode: 2500 - WPA-EAPOL-PBKDF2 (Iterations: 4096)
Speed.#1.........:  340.2 kH/s (89.52ms) @ Accel:128 Loops:64 Thr:1024 Vec:1


Then two GPUs kill performance:
Hashmode: 2500 - WPA-EAPOL-PBKDF2 (Iterations: 4096)
Speed.#1.........:  134.1 kH/s (30.18ms) @ Accel:128 Loops:16 Thr:1024 Vec:1
Speed.#2.........:  190.4 kH/s (23.62ms) @ Accel:128 Loops:16 Thr:1024 Vec:1
Speed.#*.........:  324.5 kH/s



Tried to go for three GPUs and the system won't boot up, simply hangs on a black screen. 

Ideas?