It sounds like a good plan to me.

I always suspend the Agribon over PVC or EMT hoops to hold it a little above the plants. Those sturdy hoops also provide me with the option to throw a heavier cover over the whole thing if bitterly cold weather is expected with temperatures lowers than what I think Agribon-19 and plastic alone can overcome. I have 7 old blankets folded up in a pile in the garage that I can toss over the row cover if we're headed towards the lower 20s.

If a freak snowstorm or sleet is coming, I fill up milk jugs and set them in the sun all day to heat up and then slide them under the row cover at mid afternoon. My ground slopes too much to use Wall-O-Waters, but the milk jugs work about the same way, particularly under row cover and plastic, and can keep plants surprisingly warm.

Using row cover is one of my favorite techniques as it removes the worry factor and lets me sleep well on cold nights once the plants are in the ground.

Even after my row cover has a few holes, I keep it and use it as an interior cover thrown directly over the plants under the row cover that is suspended on hoops, giving them two layers of protection. Sometimes I just throw it off to the side when the crisis is over and leave it stretched out lengthwise beside the plants, but under the suspended row cover, so it is easy to put back on if I need it again.

Plastic gives protection from wind, rain, and snow, but I think what you gain in temperature is mainly from the ground being heated by the sun during the day and holding onto the heat and able to give it off at night. I don't think you would get as much benefit from the plastic if you were just adding it for another protective layer for the night. Understand, this is not scientific, just my thoughts, but if I have something under plastic, I still throw a blanket or sheet over the plastic if the temps are going to drop low, like Dawn does.

Last year I knew that I was going to be away from home most of the time, but decided to do an experiment. We have a water cooler/heater that uses 5 gallon jugs of water. We have a good relationship with the man that owns the company and he gives me as many broken bottles as I am willing to take. I went down and went through his bottles and picked only those that had a hole near the bottom and brought home 8 or 10 and cut the bottoms out. When I thought the freezes might be over I planted transplants in a raised bed and put a bottle over each one, with the top of the bottle left open. The bottles are tinted light blue. I left home in March and didn't come back for a few weeks. The plants were a little leggy, but not bad when I came home. They hadn't had wind, so I spent a couple of days uncovering them during the day, and covering them again at night. When I left again, and I felt the weather was stable and I left them uncovered and caged them. They produced tomatoes all summer. They were never watered, but I do have a wetter climate than most of Oklahoma. I would not say they were great producers, but they were good producers. The neighbors picked them when they wanted a tomato or two, but a lot of fruit stayed on the vine too long and I would pull them and throw them away when I would come home. I think the only thing that hurt production was that they weren't picked when they needed to be, since I was only home one or two nights every other week. These were all transplants that I started myself, so I had little to lose. I had already chosen what I was taking to the farm. Some had lost their name tags, so I didn't even know what I was planting in some cases, and in other cases I had too many of one kind. While I would not want to start all of my tomatoes this way, I would certainly be willing to try a few and be able to get early tomatoes. My average frost date is the 6th of April, I think. Average!!!!

When you are using plastic, it is much easier to control the temperature in a large space than it is a small one. I don't have a greenhouse so I only use low tunnels, and only on occasion. We have a tube bender that makes a four foot arch out of a 10 foot length of electrical conduit. My ground is soft so it is easy to push it down into the soil. My plastic and my row cover are 10 feet wide, but with the arch pushed down into the soil, it gives me plenty of extra on the sides to secure it. I think I bought the plastic from Johnny's because it was the only place I could find the 10 foot width the year I bought it. I ordered 500 feet of row cover one winter from a company that takes orders all winter, then ships all at one time in the Spring. It is probably enough for a lifetime.

Gardening for me is about good food, but also about nature, exercise, experimentation, and learning. We find it funny that each time we walk through the back yard in summer, we are bringing food in the house even after we think we have picked it all for the day. A productive garden and a few laying hens can provide a lot of your food.