Now that is a weird restriction...what sport/type of venue is that
5 inches is bonkers too, even the 24-70 at 70 is longer than that! (5 inches = 12.5 centimeters right?)
Anyway, after a quick look at TDP tables (like in http://www.the-digital-picture.com/Reviews/Canon-EF-24-70mm-f-2.8-L-II-USM-Lens-Review.aspx
) your only true choices are 24-70 II (4.4 inches) for IQ and 24-105 (4.1 inches) for reach.
You also have the odd choices like the 28-135 and 28-200 but those are old designes (late 90's)
Anything longer seems well...longer. The 70-300 DO might be a winner too but the optic qualities are...disappointing to say the least: http://www.canonrumors.com/forum/index.php?action=post;topic=21650.0;last_msg=411551
Short version: The rule is big time BS, 3 inches longer and you'd be in 70-200 territory! You gotta fight for your right to photography!
EDIT: multiple ninja'd. That's what I get for including references and having to convert that damn imperial system.