Re: economy of scale in rockets: how?

My information is a bit rusty, but doesn't the engine
efficiency also increase with size?  I think this is
related to gas flow & resistance in the nozzle & bell,
in addition to loss of heat from the working fluid
into the engine walls.  I assume there is such a thing
as too big of an engine, but there is also such a
thing as too small of an engine, no?