Wow! This is one of the best tanks I ever seen. Congratulations!
I have the low light tanks, cannot compare, but it seems to me, that in the shaded are it should be OK, just give it some time for adaptation.
Mine, the first weeks after ocean (through LFS), didn't open to feed under 200W halogen ceiling light above the kitchen counter, until shaded it by newspaper.
To make it open during daytime:
Hard to say, mine is not trained, it opens only when it senses the food in the water, and in the late evening. The fish is fed very well 3 times daily (particular requirements), and the sun coral opens in ~15 min after adding food.
It has own feedings, trying to keep twice weekly, but sometimes miss for 1.5 week, then it opens less and less.
Out of topic: can you describe direction and amount of flow and kind of filtration filtration in this tank?
I had 20g long mixed reef tank, and wasn't able to make an efficient flow, without bothering inhabitants and taking too much place for the flow areas, where nothing can be placed - in full blast and not to block flow, if it makes sense.