Thanks!  Will try...  https://www.amazon.com/gp/product/B01EUW4F4K/

None of my GPU cards will fit into it due to the 1x slot's back end stopper, so may it be cut out so the 16x card will fit into the slot?

1600w 80+ Plantinum:  https://smile.amazon.com/dp/B00R33ZBQU/  
or, get 2nd PSU then short green to black:  https://smile.amazon.com/gp/product/B01C7Q4MJY/  

Any, plus  
http://cyclone.com/products/expansion_systems/600-2710.php  
($3600 internals; $4600 complete case+pws) plus      
https://smile.amazon.com/gp/product/B01CEKN5VO/  

What is a good 7 GPU motherboard?  And case with enough space for air intake between the graphics cards?

Tested GTX 1080 Founders Ed. with everything overclocked (with MSI Afterburner) to maximum possible without errors and it tops out at 451 h/s with average ~425 h/s (with ccminer); 'also elevate priority of miner task to ABOVENORMAL to mitigate intermittent slowing from Windows system background tasks that run at NORMAL priority, such as the TiWorker update task.  'anxiously await Linux Claymore so we can run eight AMD GPUs instead of the Windows max. of six.

What causes 'Invalid Share' to be sent to my mining pool?  I have a few so far.  They deduct some from my total when it happens, so I want to prevent or reduce it as much as possible.
[UPDATE] I researched this problem and it is usually overclocking errors or bugs in mining software; others have posted that this miner may send them, though typically only when combined with certain GPUs.

I was guessing h/s.

With an RX 480 Sapphire Nitro+ OC 8gb stock-settings mining XMR I get 645 h/s; I took recommendations from the Eth. board and overclocked memory by 200, reduced Voltage by 48 which resulted in a stable 724 h/s, 'good enough.  Well, perhaps the newest GPUs (Pascal GTX 1000s and Polaris RX 400s) and their drivers are in line for mining software optimization by some crafty programmer.

Is it typical for all RX 400 series cards to mine XMR with a maximum hash rate of ~550 h/s stock like with my 470 & 480 cards and the same experiences of someone with similar results on the previous page?   When is it planned for this miner to take advantage of these new RADEON GPUs and Catalyst?  At least this and ccminer work with the new GPUs; I was using Minergate, but it's GPU miner crashes on RX 400s and GTX 1000s.  It's awesome that Claymore is coding a Linux version as I'm building a miner/server with 8 GPUs, 2 CPUs (20 core, 40 hyperthread, E5-2630 v4) and I'll be using both of Claymore's CPU & GPU miners.

.
RADEON RX 470 4GB connected via "Razer Core" eGPU (USB3.1c/Thunderbolt3/40Gbps) produces 550 h/s.

Is there anything I can do, other than OC, to increase h/s in Windows?  Since I value power efficiency, I use -a 2 and No-OC; however, even though I tested several -a # settings, they all produce 550 h/s.  I am using the latest Catalyst beta drivers.  I assume cryptocurrency mining consumes little bandwidth or memory?  So, PCIe splitters and low-memory GPUs should be cost-effective and have little effect on h/s?  Finally, just as a brand/miner comparison, I swapped in a GTX 1080 FE to test with ccminer and it only produced 350 h/s.