I don't know the name of the root stock that Burpee uses for their grafted tomatoes, but I'm sure they have that info available if you google it. The plants were about the same size. I bought the Burpee grafted tomato from a garden centre/grower and know that they received the little grafted plants in a 50 cell tray. They were very small plants. I do know this, the root stock and top of graft varieties need to be the same size main stem to graft them together. The own root ones that I had started were from a seed supplier that I mail order seeds for many years. The germination was excellent and the seedlings were very healthy.
I do have an oscillating fan in the gh and it may have affected the pollination of the own root. I have adjusted the fan to see if it will make a difference in the own root plant for setting fruit. But as far as actual plant size, the grafted on is several times large, (not in height, but in more vigorous and bigger side branching). The plants were planted the same depth since there is limited space in the self watering set-up. Graft is about 1-1/2 inches above soil surface
This is a photo from June 24
