My fear in cross flow is that when the bottom half of the radiator is clogged in mud, those rows would not be cooled at all, whereas a down flow rad would at least get SOME cooling (in my case, I got an extra large radiator thinking of excess capacity to cool even if part of the radiator was clogged; I still think I would overheat with half the radiator clogged, but I can probably get by with a third of it clogged).