Binford, I put my tomatoes in my greenhouse (planted in the ground) a good month to 6 weeks earlier than I could put them outside; I do cover them for a while with a large, clear-ish garbage bag over a ring-type tomato cage (with ventilation in the top - which is actually the bottom of the bag), and also put a jug of water near each plant, under the covering, which helps keep the temperature more even; other tender plants get covered with Reemay at night.
Even if you don't plant all that much earlier, the temp in the GH warms up much faster than outdoors, and your plants are also protected from wind. It will probably take a little trial and error to find what works best for you.
