I usually fly short distances which doesn't require more than the 1000 lbs. of fuel in the center tank. My question is - do I need to have the crossfeed valve open or closed during the cruise phase?-Mikkel

Mikkel - X-feed valve should be closed during normal conditions. You have it open if you are EO and want the remaining engine to draw from both tanks to aviod imbalance, or when you are rectifying any fuel imbalance between the main tanks.Hope it helps,