tomato supports - where to tie the twine

I'm not really sure where the bottom of the string is tied in this type of tomato support, which I am using for the second year. Last year I tied to stem of the plant. This year, I tied the twine to a pole weighted down by a brick. Works well so far. Does anyone recommend another method?

My plants are tiny this year. :( Not enough sun. I won't grow tomatoes in these beds again - until a tree or two comes down.