Not sure if this is the best, but this year being in Zone 7 around Philadelphia, I noticed the night temps hovering in the low 40s and the day around 60 but then some days goes to 80. Now I ordered 9 plants from Burpee which should be delivered tomorrow but still need 2 weeks about to harden off, so I couldn't wait and bought 2 Early Girl plants from a nursary about 10 inches high when bought about 3 weeks ago and the photo will show you one of the photos I took today, the other is the same. I only fertilized them once with half a portion of solution of Mir Grow w/s. Sorry for poor photo this was from my phone.

My Strategy was to pot them up into 5 gallon vinyl bags with about 3 Gallon of Potting mix (I did this so it was easier to bring in at night ect...) and once the weather looks clear pot up again to my 25 Gallon fabric bags with the same potting mix. I was gona go to plant them straight in the 25 Gal bags but thought it would be too much effort to carry indoors plus tracking mud inside. The Vinyl bags I just leave on the porch which faces southwest and gets about 5-6 hours of direct light..

Now the cool part about this if it works out, I don't think the plants will get shocked, because number One I don't leave them in temps under 50f at night, 2) my strategy for repotting in the 25 gal fabric bags is to pour an appropriate amount of potting mix on the bottom then place the vinyl bags in, then just cut around the vinyl bag and tear it away then add rest of potting mix. 3) in a storm I can still bring them in or let them take cover. My reasoning for this is that I knew they would be getting big and were starting to outgrow there 3 inch pots and I did not want to risk anything to get early tomatoes. I estimate that I should have my first ripe tomato around June 15th with the current weather situation.

Now I am not the most creative color in the crayon box when it comes to gardening, but i like to expermient. Let me know what you think and I will keep updates and also show you the comparison from these two early girls to the other two summergirls which are on their way. I know they are not identicle but close enough to compare.