I just bought an ergo performancec for DS2 and it is really uncomfortable to wear.
I had him in it for about an hour yesterday and my neck and shoulders were aching.
He is 6 weeks old and weighs just under 5 kgs. I am average build, size 12, 165cm, small boobs.
I did a lot of research and it looked awesome. I want to love it like so many of you.