First off, I don't mean to derail the thread but hopefully add comments and thoughts to help you on your journey to come up with the best setup possible and I think you're doing a great thing for the community by developing this radiator. I hope my comments are viewed with good intentions and helpful and not critical or negative.
Nick would know for sure but I think radiators whether top-bottom or cross flow typically have the hot water enter the rad at the top and then exit cooler out of the bottom.
You're right that the FXMD car has proper ducting and does not have A/C so it's not comparable to your car (does Jim's have AC?). However, proper ducting probably has no significant benefit at idle or stop-and-go traffic so the ability to cool at idle during hot track days after a session is somewhat relevant. A/C units do release a lot of heat infront of the radiator which effectively is like raising the ambient temperature from the radiator's standpoint. So a non-vented hood and A/C would probably be the most demanding for a fan setup -so you have a valid point there.
I believe the higher the fin count per inch, the higher the fin density, the better it cools due to more surface area of the fins, but having the downsides of plugging up from sand, small rocks, dirt, etc...
As far as fans go, It would be good to know the CFM capability of the stock fan and then compare that to the CFM of your specific 2 fan setup. Which fans are you using by the way? In general, fans pull a lot of AMPs and it's probably better to not tax the alternator by using 1 fan if you can get away with it from a more efficient layout. This is why i've been asking about your fan test conditions and mounting because as my previous post said, if you just remove or disable one of the fans on Jim's radiator shroud, the remaining fan would suck air in from the gap between it and the radiator face and not effectively cool the radiator where if it were mounted directly to the rad, all of the fan's CFMs would pull directly through the fins might be enough to cool it.
Again, your hard work and development is great and I too will be in need of a good radiator so i'm also trying to learn or help you any way I can to develop your setup to have one of the most efficient and effective packages out there.
