Thank you all so much.
It is not so much the full/empty paradox that I find hard. My own preference is to interpret it as Wang Bi does as the Dao being "full of emptiness" (comment ddj ch 45.1). Rather it is the link with 'function' that I find puzzling.
I found Taomeow's link to MA very elegant; but it makes me a little itchy to interpret a text in the light of a significantly later practice. That is not to say that there is not deep wisdom and insight to be found in taiji; merely that I remain a little sceptical about using it as a lens to understand the daodejing. It strikes me the text is looking to something deeper and broader.
Anyhow, lot of wisdom's been thrown my way. Will be taking some time to ponder. As things stand I feel a bit like the Yellow River meeting Lord Jo of the Ocean...