Nothing to excuse yourself for Richard because it's all pertinent and intresting. There are a few points about your wheelbarrow project I thought I'd bring up. The one was the question you had about that old picture where the wheelbarrow is standing. I mentioned the arched bow - using some boat terminology there, but a boat and a wheelbarrow do have much in common if you think about it - and that this is a very practical design element that will increase the carrying capacity. It's just that if you notice, and even other wise, if the front side of the box of the wheelbarrow rises from the sides toward the middle forming an arch, you can stack a higher load of say potatoes from the garden in there without adding proportionally so much more weight to the wheelbarrow as a whole.
And concerning the weight of the wheelbarrow, which, lets admit is a bulky thing as it is, when I rebuilt mine I used poplar wood for the box rather than pine, meaning that I could have even thicker sides and still come out lighter in weight. On top of this advantage poplar wood, being made up of extra long fibers is exceptionally resistant to wear and abuse and was used as floor wood in boxcars and for the floors in hay lofts.
While pine was the primary wood in my old wheelbarrow all of the braces were carved from oak and the frame work of the box was also oak, though I don't see why there other than for durability. These I faithfully replaced where needed.