Assuming you have more time at where you are living or during the off season... that's a great idea to build the walls ahead of time. I bet that 1/8 inch could have been wood shrinkage. I couldn't figure out why you were in setting the walls until I daw the roofs along the sides. Awesome 👍
I made it a point to take one day off of work a week where I spent building the walls. And over the 4-5 months that I couldn’t make it to the property I was able to get 80% of the walls built. This was especially nice that I could do them inside a heated shop and avoid the elements.