Wow! This pertains to the question I was going to post. When you have a milk carton full of seemingly hundreds of seedlings do you transplant each one separately? This seems like tedious back breaking work.
The difference I see between your system and the milk jug system is that with milk jug type containers your'e creating a mostly self contained micro climate which will draw in and hold heat and produce some water, making an earlier sprouting possible.
Your idea, from what I can see, would not have a micro climate so your seeds will have to depend on the weather to warm up and you'd have to watch for watering. So if you want a head start on planting you'd have to start them indoors under lights or go the milk jug route.
Do you wrap the flat in plastic or have some other way of getting the heat retaining moisture producing micro climate needed for early sprouting? I like the idea but must be missing something.
I'll know better next year! Thanks for the article. 
