Actually tried some Zcash mining on that computer, it's possible to do mining with the GPUs. Got into crypto currency mining last Thursday, Zcash is another currency just like Bitcoin. Works great on my home computer that has 3 Titan X. When I do it on my x4 GTX 1080 Ti, it crashes every second hour or so. Not that the computer crashes, but the GPU's stops working. What gives?
On Monday, I could do some testing in removing one of the GPUs. See if it runs smoother. Have you tried running with only 3?
If that IS the worst case scenario. We would just have to buy a eGPU holder, use it with a Mac laptop or iMac with High Sierra when it releases.