Hi Slug - (hey - catchy name!) - The bad news: if you look at my recent posts you'll see that I've taken the car backwards & forwards to the dealers (who've been really good) but with little success. They've replaced everything there is to replace - but the rattle keeps coming back.
There's no doubt in my mind that this is a design fault that Audi really should address - but probably won't.
The middling to good news: Don't waste time with ordinary silicone - it's totally useless. The BMW product "Gummipflege" - however is instantly effective - but the effects seem to wear off quickly (within 24 hours) & the rattle comes back - albeit greatly reduced.
HOWEVER...I have a theory that it is crucial as to where this stuff is applied and I'm currently conducting some experiments (yep! - I sound like a complete loony). Certainly the seals around the door & the door cavity are important - but my latest theory is to treat the "groove" in the seal running along the top of the door. This seems to have worked on the drivers door and I've just treated the passenger door. So I should know the effectiveness by tomorrow evening. I'll let you know...
regards steve b