The dimensional lumber plan seems way overkill. For me anyway. I like my stuff to be as simple as possible.
I built mine using the roundwood plan. I did change some things to make do with what I had on hand. It has only three legs.
My yoke is round and is lacking a notch, this will cause your work to shift around sometimes and that can be frustrating. I should change this but I'm lazy and it is still very usable. I really enjoy using my drawknife on that horse.
I used rope as an hinge and I use various blocks to get the right angle for the support. There is no metal hardware on it simply because I didn't have any.
If I was to make another I'd use something like this design:
This is from "Le Village Acadien", a tourist attraction of the region. I think they used this design to make shingles.
This is the part that I like from the design, there is no treadle frame. The fixed angle for the support is limiting but this should be easy to fix.
A detail of the leg joints.
If you end up building one, I'd like to see it.