At this point I've had to move the lettuce out to the greenhouse because it was getting to tall. I would still be ok, if the top of the pots was the same level as the bottom of the cold frame. I installed an automated opener since I shared the last set of numbers.
What next. I would like to build a small box that this can sit on top of so that the top of the containers will be at the bottom of the cold frame or just below it. This would also allow me to hold in more thermal mass to help stabilize the temperatures. Once that gets setup I'll consider adding a grow light and an warming light as a heat source to get things started earlier next spring. Until then I'll be enjoying my fresh tender lettuce and green onions.