My big tomato seedlings, and what to do with them

As I feared, my tomato seedlings started in March are big! Here's a pic:

And here's a comparison between Early Pick, started in March, and Sugar Lump, started 3 weeks ago:

The good news is that by using several strategies, including pinching back the main stem to encourage branching,  blowing on them with a fan to build strong stems, and feeding with dilute fish fertilizer every two weeks,  I am keeping the older seedlings strong and healthy.  I don't  even need to to stake them yet.
Early next week I will start hardening off my biggest tomato plants by carting them in and out of the garage in a wheelbarrow for steadily increasing daily exposure to wind and sun.  There are 3 varieties: Mortgage Lifter, Early Pick, and Rutgers. Around May 5th I will put a few into the garden. I'll either have really early tomatoes or lose them to frost... It will be an interesting experiment.