I'm sure you're not wrong! If I make it happen I'm happy to facilitate making them available, but there are definitely some technical hurdles which have prevented me from already jumping in with both feet. Just to show that it's not me being lazy with a bs excuse not to help some fellow jeepers out, below is a summary of a few pits I've run into thinking through this rabbit hole:
Our coils are generally applied in large commercial and industrial HVAC equipment with higher expectations for longevity, so the construction differs. We build mechanically bonded round tube/plate fin (RTPF) type cores and braze the coil tubes into a main header/distribution tube.
The automotive industry for decades has used the flat tube with accordion fins that get brazed together in an oven, that we're all familiar with if we've seen a TJ heater or radiator core. They are less robust but also less expensive to produce in large quantities and can pack more heat transfer capacity in a small space, both of which are attractive features to an automaker who buys them in 6 figure quantities per year and only needs them to last through the bumper to bumper warranty.
All that to say it will be challenging to match performance when constrained to the same dimensions, and even more so if I lose cross section to make room for header tubes. Going to copper helps some, and some testing would show how sensitive the water pump and blower fan are to increased pressure drop to see if there's room there to get some performance back.
For example, if we're already out on the right of the water pump curve and it happens to be reasonably steep, then that means the flow rate (x axis) would be more tolerant to increased fluid pressure drop (y axis). Flat would be very sensitive.
Fans have a different shape but the same principle applies. Not only do we hope to be out to the right for the reduced sensitivity to pressure drop, but we also want to stay out of that hump area where 2-3 different volume flow rates can result from the same pressure, because it likes to switch unpredictably back and forth between the solutions, making lots of noise and possibly damaging the fan.
