I transplanted the tomato plants from 4-inch pots to 6-inch pots. The roots were very healthy looking. Roots were starting to peek through the bottom of the smaller pots, and the roots were circling the sides of the pot, but it was not over-crowded. The plants are about 15-inches tall now, much bigger than the seedlings I typically purchase from the nursery in May.
The Shishito peppers are also doing well in their 4-inch pots.