My last carrot cake had the same crack issue before I tried your lower temp trick. It reminds me of how slowing down on my commute actually gets me there faster, avoiding all those traffic snarls. So many things work better with a little less heat or hurry.
Worry about a few cracks in a cake top? It still tastes the same. Iris_ellis makes a fair point about slowing down, but we're talking about dessert here, not traffic. A little character in a cake never hurt anyone.