To Mark and Rob,
 Everything you both have stated above has been my experience
also. My skepticism regarding it's operation as related to real
world 727 fuel system is what prompted me to ask about it.
 I have had no trouble balancing tanks (as long as #2 level doesn't
go below #1 and #3); however as you've pointed out, I've found
it necessary to routinely cycle the boost pumps off/on to ensure
a reasonably balance fuel load :)
Thank you for your great explanations.
Ken