If it's any help my health nurse said that overheating is a problem, not being a little cold so don't over do it.

I haven't used my grobag yet as it's too big and it's a summer weight one but I've used a few other sleeping bags. They would be similar to a 2.5 tog I think. I dress Brock in a short sleeved all in one suit or singlet with a warm fabric long sleeved and legged all in one suit. I don't place a sheet or blanket over him. Our house is pretty warm though and it probably wouldn't go below 16 degrees over night. He has comfortably slept that way since he was a couple of weeks old.