Wouldn't it be tricky to route the tubing with the side rad on the mobo side? I imagine that the ports would face the PSU, and two rotary 90-degree fittings would require ~28mm of clearance.
I really like v1.1 layout with the side rad on the GPU side. Routing the tubing is pretty straightforward, just need a proper mounting bracket and a few extra mm of clearance.
One key issue, performance.
A 280 or 280 against the GPU water block will restrict airflow more than the Mobo side. For the same dual radiator setup, you will loose some performance.
This is why it has to be on the Mobo side to get the most out of it.