Clarification on powering GPU & Riser off same 8+6 PCIe Cable

[bhest]

Hi all - long time reader here but first time posting anything

I'm running 4x gigabyte 1070ti that require 8 pin pcie. My risers are 6 pin and of course I want to avoid Sata. Can I power 1x riser and 1x gpu off the same pcie cord that contains an 8 and a 6?

PSUs are 2x EVGA 650W P2. I'd run two cards and two risers off each.

Other option is to order molex risers but wanted to see if that was truly needed and save the 50$ if not

Thanks!