Sabreliner--
True what 328dude said, you can show up at the gate and they'll be happy to accomodate you. If you want a little bit more of a confirmation, you can call 866-SWA-PLAY and find out load information through an automated system. Keep in mind that I have gotten on many flights that were listed as "bad" and every flight that was listed as "good." After wading through the automated menu, you have a chance to list yourself on a flight, which makes it easier for the gate agents to accomodate you. Any problems with the system and they'll give you another phone # to talk to a live person to list.