Two power cables for three risers and four PCIe cards

I am using a PowerEdge R740. I want to use 4 PCIe cards and provide them with AUX power.

I have enough power supply capacity and GPU kit for power cables.

Each power cable has two connectors; one with 6 pin, the other is 8 pins. Each type is good for me. Hence, with 2 connectors on 2 power cables, I have 4 power connections, which is good.

For all cards on PCIe x16 sots, I have the following configuration:

• 1 card to Riser 3
• 1 card to Riser 2
• 2 cards to Riser 1

The problem is how to power up all four cards with the AUX power cables. Apparently, the cables are made to power up only the cards on Riser 2 and 3. The connectors on the motherboard specifically have label indicating that. Besides they are short to reach Riser 1 side.

I am thinking about —by accepting the whole risk— cutting the cables and extending them, such that

• Riser 3 cable to power up the two cards installed at Riser 3 and 2
• Riser 2 cable to power up the two cards installed at Riser 1

I wish to ask if anyone can comment on the feasibility of this solution? 

Kind Regards,