If the soil is overly saturated you will get root rot. The plants can't store it all and it will make it hard for them to breath. It's best to keep the soil damp.

sg,

I would say yes. Unless you use swamp plants. I have experimented with Earthtainers which are twice the size you have stated. 5 inch soil column was used in those and the soil was too moist too long. The tomato plants did well at first but after awhile suffered from too much soil moisture when the soil consolidated over time and lost its air entrainment ability. My next experiment, I used nylon rope to move water into the soil volume with three ropes of 5/8" diameter and even this seems too much. I believe a smaller rope system will work but at the start I will water conventionally until the roots get going and the plant growth starts to take off. Then let the system water from below. I also use an automatic water float valve in the reservoir and this has worked well. Gardening is experimental process. Let us know how it goes. JMHO Aloha