Which 70-200 to rent for a street event?

Hi all,

Camera is D700.  I want to rent a 70-200 for a cultural event, Charro Days, for the first week in march.  This will be mainly parades, but I want to do candid shots of the crowds.  So we come down to 70-200 f2.8 or f4.  It's going to be hot and I'll be doing a lot of walking, so the lighter weight of the f4 might help.  Either lens is going to stand out and be obvious, nothing subtle here, but I might be a little less conspicuous with the f4.  Downside for the f4 - my version of photoshop is CS5 and I doubt the ACR has profiles for this lens.

I may print as large as 18x24 for fine art gallery display.

Thanks for comments and suggestions.

--
Gene in Deep South Texas
http://www.pbase.com/lahuasteca/