I would get whatever McClellan you could locate.  As I alluded to in my
post, I cannot tell the difference between the 11.5" and the 12" and switch
from one to the other without notice.
I have a friend who is about your size who rode in an 11" McClellan while
another friend the same size was just as comfortable in the 12".  I don't
believe it makes much difference, at least not in my experience.  I have
plenty of room in my saddle for me and my fanny pack.  I think it is just
what you are used to, but I don't think 1/2" makes that big of a difference
in a saddle without padding or flaps.  After all, many people customize
with different leathers or seat savers.
Teddy would be a good person to answer this question....  What do you
think, Teddy?  Do the McClellan sizes make a big difference to you?  I know
you rode yours with a seat saver.
Shannon Loomis and Quail Meadow Star