Air Classics I believe ran an article on Beguine a few months back. They said that on the ground, they'd have to spray water through the radiators just so it wouldn't overheat, as the radiators are located outside of the propeller's flow. I personally don't see the advantage of the tip-mounted radiators. Just imagine the weight of the extra plumbing and extra water volume required to fill the system. Also the large stresses put on the wing because of the extra weigt at the tips. I'd be willing to bet that just one of those tip radiators has as much drag as the conventional belly scoop.