I had not heard of the one arm holding the baby form. I thought only hung fut had a one arm form.
I had lost the use of right arm for almost a year (after i was struck by a car while riding my bike). I started messing around developing a left hand form for my personal practice. It sounds like this one arm form could have aided my practice back when. Luckily that was years ago, and i am all healed now (save for one kinda badass scar

Walter