Yeah, I'm aware of the inefficiency this approach has but I'm working with what I have atm. In any case additional fans can be added to either the side panel, rear exhaust in reverse or at the bottom near PSU for additional cooler air. Running the top rad in reverse is also an option with the mentioned fan option as exhaust.
But my question was more in regards to the fluid dynamics and pump's optimal workload considering A & B layouts. We have gravity as well as flow variation between blocks and rads so I'm just curious to know yet couldn't find any info touching on this.