Andy
I'm afraid the Audax has a weight limit of 95kgs (209lbs). I found this out when I made enquiries with Thorn myself when considering a faster alternative for day rides than my Nomad. I'm 130kg and I've had zero problems with my Nomad and I've just done 10 000 miles in my 18 months of ownership. I bought it for touring but to be honest 95% of my riding is day rides from home and back at around 1000 - 1500kms a month, riding anything between 30km on a very slow day or up to 200km in a day if I've feeling adventurous. (Admittedly I've only done one 200km day ride since I've had it, but I've done dozens of 100km plus day rides on it.)
When I'm riding along with my Schwalbe Marathon Mondials at 50psi the bike felts quite fast - it is only when commuter and the racing guys overtake me that I realise I'm not, but at least the bike "feels" fast and not sluggish.
Sorry, I know this wasn't the reply you were looking for.
Tony
NZ
P.S. Re reading your question you want a Thorn for Audax riding and I guess the Nomad it too heavy for that. Thorn did tell me their Club Tour didn't have a fixed weight limit. Just email Thorn, they always reply to questions like yours, as they did for me.