I run a bunch of them with 5 GPU's each with no problems using USB 1x to 1x Risers.
You only need to plug in 1 GPU to the monitor so you can see what's going on. After it's all set and automated, no need to plug anything in.
Use a remote desktop software like teamviewer or gotopc, etc...
Make sure you're using a GOOD power supply and plug in the MOLEX cable into the Mobo.
I use platinum power supply as my power consumption is very high for each rig. So save some electricity.