I only have one concern: do you think coolant would flow from bypass to T in hose 15 and go back through the radiators, out hose 16 to w/p? Or do you think it would maintain its flow from bypass - T - w/p? (I know thats mouth full)Fluids will take the path of least resistance, so, no, it wouldn't do anything like that. While there could be a small amount of movement between the radiators, it's very much easier for the fluid to flow from the T straight down to the pump to fill the void created by the fluid being pumped up to the head. At worst, I would think you would have a "blended flow" condition, with maybe 30% or less flowing up into one radiator and out the other. Bear in mind that the bypass hose will be smaller already, too.