Wow, that is interesting! Never thought of pull-ups in this way. What you figured out makes perfect sense, however, I have seen way too many super lanky guys who had no troubles with pull-ups at all. But this gives you hope Eve :)) Dont give up. Back in the old days when I was in my 20s and was working out hard, I could do 30 pull-ups in a row (177 cm / 77 kg) and based on the videos of you I have seen here, I am sure you will master this exercise too ;) Hang in there! :))