R740xd Riser Power from internal drive backplane to GPU

So I have an R740xd with the 4 internal drive bays/carrier. My single PCIe riser does not have power on it. I bought the riser power to GPU PCIe power cable. I looked at the headers for the riser power cables and they are the same as this plug. However, one pin is blank coming from the internal carrier backplane.

Both of the riser power headers are being used: one by the internal carrier in the front, and one by the rear drive bays.

If I wanted to get rid of the internal carrier, could I use the riser power from that for the GPU instead?

I don't want to fry the board or anything by doing this, so figured I'd check first.

https://imgur.com/a/Qoy8Nxf

In the pictures, the white cable is the current one for the drive carrier. The black one is the GPU power cable I want to install. I am referring to the "RSR2 225W" header on the board.