I learned the sunny window thing the hard way. My first rack went up on the wall right next to the window since it was the only open spot, and it looked nice with the light coming through the bottles. 6 months later half my reds had gone orangey, and a couple of the sheer pinks were syrup. Now it’s on the wall behind the door where it never gets direct sun.
Also glad to hear someone else had to buy a second rack. I keep telling myself the first one is almost full and then find room for three more bottles. Is your second one stacked right under the first or did it end up on a different wall (see this thread)?