When all other things are equal the path of least resistance is often the shortest. That's why i'm suspecting that this configuration is not using 100% of the resources of these rads. Water in outer channels will 'stagnate' relatively to center channels,which will see the highest water velocity.
That's the usual 'array' problem that Axle faced with his passive rad, BTW.
Code:
water in>--+-------+-> water out
| |
+-------+ (1st parallel pass)
| |
+-------+ (2nd parallel pass)
in this example the 1st pass will see most of the flow, while the 2nd parallel pass will see far less flow, because water has to take a longest path - thus a path of higher charge (=flow resistance).
Code:
water in>--+-------+
| |
+-------+ (1st parallel pass)
| |
+-------+-> water out
In this one each path has the same length, and will see the same flow.