It was who?
Legend has it they won't be on tour with Don this summer as they're still introducing their songs in Cork.
I went for the Cass County t-shirt with a massive photo of Don on the front and seven European tour stops on the back. I'm presuming they were US sizes as I went XL and it fits me like a parachute. I tend to buy a t-shirt at every concert I go to, incidentally the two worst acts I've ever seen are also the two best band t-shirts I've ever got.
RCF - There tends to be at least one person every concert who will shout something, if you're feeling brave you could use that as a sort of litmus test, if people laugh and Don doesn't look too bothered then you could probably get away with it. The only other thing you really need to know is no phones at all during the performance (that got extended to the support act in the UK). Most of all, enjoy!