I practice SFG so I grow vertically as much as possible.
G welded re-bar into an upside down U shape. The post just fit in the inside corners of my box. For my indeterminate tomatoes I hang twine from the cross member to the ground and train the tomatoes up the twin. Yes I pop off the suckers. I plant 4 indeterminate tomatoes across the side of a box.
For cucumbers, cantaloupe and zucchini I attached hog wire to 2 uprights with zip ties. I "assist" the cantaloupe and zucchini by loosely tying them to the hog wire with strips of old stockings or t-shirts.
Since peas are very light your webbing between 2 uprights would be perfect.
I like using the re-bar and hog wire because it does not need to be replaced. It is also easy to pull out and move from one box to another for rotation (tomatoes).
My brother made elaborate frames using PVC. He ended up having to reinforce the uprights with re-bar. The weight of the plants and fruit and the heavy winds associated with our afternoon summer thunder storms caused his PVC frames to fall over.
I TOLD him to use re-bar!
"Little Brothers" do not listen to their "Big Sisters".