I've tried 10 different cultivars, including arakawa, without luck. I'm not sure it's the sun as much as the lack of humidity and the dry wind that does them in. If I had the room, I would buy a cheap greenhouse, whitewash the panels, and use it for my maples and other 'tender' deciduous. This summer was brutal... even my elms were getting crispy.
Even two japanese maples I had planted in indirect sun next to a koi pond dried up and died. I replaced them with a camellia, and the camellia is thriving in the same location.