My third baby, a boy, is now 12 weeks old and still doesn't like (he hates them actually) ANY of my carriers. I have a Moby, a ring sling, a Freehand Mei Tai and an Angel Pack LLX. I used the ring sling daily with my first baby until he was bigger and then an Ergo, and I used a Moby daily with my second baby and then the Angel Pack when she got bigger.
His reaction is always the same - crying loud and arching when being put in the carrier, and then continued crying despite walking with him and rubbing his back, which always worked to calm down my first two if needed. The ONLY way he will stay in there is if I run the vacuum and then he is quiet and falls asleep eventually, but as soon as he wakes up he is furious. I have had the most success in the Moby as I usually put him in there while vacuuming (which needs to happen often in our house with two labradors) but he's still not happy enough in there to be able to wear him while shopping which is the main thing I need to be able to do!! I have watched the Moby videos many times to make sure I am using it correctly. Having his feet tucked in or sticking out makes no difference.
He is now 12 lbs at 12 weeks so he's a skinny guy, but also quite long (24.5 inches). In the mei tai I tried putting him in with his feet tucked under him and also with one foot out. He seems too little to have both feet out. I felt like he was just too small for the Angel Pack. I have used the ring sling the least as I don't find it as comfortable.
Any tips for me? I really *need* to be able to wear him to save my wrists and get things done, esp with two other children to care for!!