When we printed Quin according to the recommendations of 3dkitbash, I still had a problem with the arm pegs. They printed too small and fragile for me to even insert them into one arm part, my less both. They always broke. The attachments looked just like the functional leg attachments. They are similar to a tiny “x,” I referred to them as “chromosome-shaped.”
My amazing husband took to the 3D modeling and fashioned a set of pegs that might work better. These pegs look more like “pegs.” They allow for rotational motion of the arms as well as a firm fit that audibly “clicks” into place. He has now posted these pegs to thingiverse.com in the event that anyone else runs across the same problem.