[Flanders]

Well, it sounds like you're out of the woods so to speak so this may be of limited use, but I am keeping a smaller squamosa under an AI Prime HD in an 18" tall tank and it's growing very quickly, so I imagine with the Kessil you will be just fine. Retracting at night sounds normal to me. Less responsive to shadows might be related to increased shimmer from the Kessil... the new normal for the clam is increased shadows all over the place in comparison to the old lighting.