a good tip is to get the 29 if at all possible.  The shell size between the 29 and the 29.5 is the same, just a different liner.  the tighter fit, if you can pull it off, will help, and they will break in and be larger if your foot is a bit long.
Also, as nomen pointed out, see a boot fitter.  I buy boots online, but I got a buddy who will fit me in.  IF YOU DON'T HAVE A FRIEND WHO WILL DO THIS, BUY FROM THE SHOP.  Unless, you have a friend who does it for a living, and will do the fitting for you, don't waste the time of an employee who is usually paid on comission.