Hi Tim,
Diameter is about 45 cm (app. 1.5'), depth is about 2". I poured in about 1cm (app. 0.5") of fine gravel to reduce the amount of water that might settle on the bottom (3rd Picture). So far this set up works fine for all my semps. I tried to cut more holes, but when the first plate broke I decided to go for 1 central hole as in all my other plates...
Regarding flattening of the roots my semps should not care as they originate from places that sometimes hardly provide for 1" of soil layer.
