Hi,
Bub was born in Dec and we used the Ergo Sport, through summer from birth with the heart to heart insert. I love our Ergo and use it all the time, much more than the pram. The heart to heart does support the head, we never had a problem with it not providing enough support. Might be a bit diff for you being up the Goldy with the heat but we just dressed bub lighter and we didnt take her out in really hot weather. But saying that we used it all the time in summer and she never got too hot.