Chip showed me a trick once that's supposed to improve the performance of the black ice, turns it into a 2 pass instead of a 4 pass, would go well with a 1/2" system. Goes like this.. Take your 1/2" hose to a Y, split of two 3/8" lines, one into each nozzle on the rad. Now your going, how the hell does the water get out? Drill a hole in the middle of the top middle tank, and install a 1/2" fitting there, 3/8 NPT should do the trick for that, use that for the output (or hell, input if you want, your choice).
This really does work, according to Chip, and he should know, he helped design these things.
Although the way Chip said to do it was kind go goofy, I think my idea with the Y splitter is the best way to go. You may have trouble finding 1/2" to 2x3/8" Y's, your on your own there.