I just totally recognized @Coxsackie by his chin, from a photo over on the Styleforum tumblr feed. I also recently acquired a tie that I believe is a damn close match to what Claghorn is sporting (except for being a square tip). Forumception, here we come...
I think this is one of my favorite outfits I've seen so far from Pitti this year.That and Benedikt's (of Shibumi) donegal tweed suit, since I have a nearly identical suit in the same fabric (and Erica's wide-legged grey trousers outfit - wow).
I'd definitely second the madras recommendation. Here's my pink/blue madras shirt - it's become one of my summer staples: http://www.styleforum.net/t/380371/proper-cloth-official-affiliate-thread/200_100#post_7289969
And pure linen is always good for hot & humid.