2000 Ford Taurus SE Heater Core Question

I have a 2000 Ford Taurus SE with the OHV standard engine. I'm wondering if anyone knows whether the flow direction through the heater core matters. I had to re-route the tubes for the heater core because the factory steel pipes rusted out. I setup a nice new plumbing arrangement using plastic fittings and rubber hose. Everything is perfectly leak free. Afterwards I fired up the engine and used a digital voltmeter with one end in the coolant jar and the other on the negative battery terminal to make sure that my coolant was well grounded to avoid electrochemical problems. The only difference between my arrangement and the original is that the coolant now flows through the heater core in the opposite direction. I don't see any reason why that would be a problem but I'd like to know what everyone else thinks. My heater performance is somewhat degraded but I think that mostly has to do with my tube diameters and my crossover bypass hose. I'm going to tweak the setup a little bit to get more flow through the core. What I really need to know is whether these heater cores are designed for flow in one direction only or if it flows easily in either direction.

I don't think it matters. On my '02 I replaced the pipes with flex hose like you and also reversed the connections. I have not noticed any degradation of performance in the heater.