That rig averages 4200Kh/s on XMR, but I feel it could do better. I do not have a lot of time to do tests though

. Also since GG, Wattool and GPUz all have their own way to "assign" cards it's kind of a nightmare figuring out which is which on that rig, lol.
All cores run at 1100MHz and I'm bios undervolted at -137.5mv.
Trick I use is to set different mhz in bios for each card, so in my rig left to right, i have 1141, 1142, 1143, etc.
root@rig14:/home/dallas# clocks
1: 2012Mhz * # GPU 0
7: 1142Mhz *
1: 2013Mhz * # GPU 1
7: 1143Mhz *
1: 2006Mhz * # GPU 2
7: 1146Mhz *
1: 2015Mhz * # GPU 3
7: 1145Mhz *
1: 2014Mhz * # GPU 4
7: 1144Mhz *
1: 2011Mhz * # GPU 5
7: 1141Mhz *
Then I know GPU #2 reported above is the furthest card on the right, GPU #5 is furthest left

Or simply read mobo's specs and find out which pcie is connected to cpu and which to the northbridge
most common order is PCIe x16 is where GPU0 sits, looking at the DVI/HDMI connectors on the left of GPU0 is GPU1 and on the right are GPU2,GPU3, GPU4,GPU5, in that order.