Bee, great idea about the understory, I was just wondering if my plan was going to work out and that I could be running out space.
I'm also thinking of covering the whole thing wit plastic, making a rectangular "hoop house" to give me an earlier start. If leave the ends open it should be much warmer without being to warm. Last frost is April 15, but some years I could have planted out on March 15 and been OK. Never tried this before, will it work?
Here's a closeup: