Hi everyone-we are prepping for the big arrival day and are working on building the body buck. We are following the plans from FFR, but we noticed that in the picture in the manual (on page 23), it seems there are some additional support pieces that are not mentioned or listed in the the blueprint plans for the buck at the back of the manual. Are those needed/recommended? If so, could anyone please explain what those support pieces are? Should we add them?

Sorry if this is a novice question-I'm the mom in our family of four that will be building this car and I'm in charge of figuring this one out (this is my first post)!
thank you.