Ours is 5 months and we haven't done it yet. It's an absolute pain! But we use the baby Bjorn carrier when going outside x
My little girl is 4 months and is in stroller, she was too nosey and she has got really good head/neck strength however I just don’t put it as high as it can go, she’s on a slight incline and then when needing to sleep, I can always lay it flat x
I sat mine up at 3 months in the stroller. She always hated the laying in the bassinet part. It wasn't at the max level tho just a small incline