Not sure if anyone is still running 2011 Macbook Pro 17", but recently this got pretty exciting for me. I boot Windows 10 with both GTX 970 and internal Radeon 6750M working. Amazing scores on 970 on external monitor.
I'm dual booting. Running Windows 10 in bios (legacy) boot mode with regular bootcamp upgrade from Windows 7.
Akitio Thunder 2 PCI-e (powered from PSU using barrel adapter)
Rosewill gold PSU
EVGA GTX 970 FTW+ plugged directly into Akitio (no riser), and latest Nvidia Driver (364.51 win10 64bit). Macbook Pro has all bootcamp drivers installed and working (internal Radeon 6750M fully working, sound, etc).
Booted into Windows 10 with eGPU fully working. Ran several Steam VR tests and score either very top of "Capable" (yellow bar), or into low end of "Ready" (green bar).
Only drawback is I have to boot using the timing method. Have Thunderbolt cable plugged in, but PSU powered off. Boot holding option to the boot selection screen. Hit enter on Windows, wait 3 seconds, and power on PSU. Works reliably for me. Sometimes I miss the timing, but just try again. It's like a 3 1/2 second wait for me before hitting power switch. Then I'll see windows boot cursor and know I got it.
First install: Boot with eGpu plugged in. Download Nvidia drivers. It should detect card and install. If not, try again.
First boot after installing drivers: Device manager showed 970 installed and active, but no image on external screen. Used Win+P to extend desktop and to my surprise external screen came alive and is absolutely kicking *** running benchmarks.