Jonathan,
I too thought that 300 grams a week weight gain was great, however, the
clients doctor and the child health nurse both thought otherwise, that
is why I asked for Lactnetters opinion.  I have been assured by the
local child health nurse that 35 grams a day is expected, this is what
they have in their manual she tells me.  I did tell the mum that I felt
the gain was good.  I actually told the mum that I think the problem is
lactose but just told her to try and keep feeding for longer before
offering the other breast, I didn't tell her to only use one breast as
you suggested, so will try that.
Val in Busselton, Western Australia
RN RM IBCLC