This is something that's really saved me and allowed me to water much faster. Concaving the top will force the water to funnel towards the center leaving a dryer perimeter. I have actually watered 2 7 gallon pots (without a plant in it) with 2 gallons of water. With and without a concaved top. The flat top bad a much more even saturation. The concaved was soggy in the middle and only damp on the outer edges. The solution!! Add 2-3 inches of coco on top. Coco always stays soft and fluffy. Soil compacts and becomes harder to absorb water. The coco acts as a sponge that evenly passes the water to the soil top. Funny how I stumbled across this too. I was filling a bunch of pots when I ran out of soil. Never used coco but wanted to try it. This bag I had sat for months unused, when I realized I was short on filing the last pots I decided to even them all out and use the coco to fill the remaining. The first water was a treat! Since I have grown close to 75 plants this way and love love love it!