it's funny you ask that. lately i'd been using dumbbells, but yesterday i used the barbell for the first time in months and hit my belly on the first rep. i didn't realize how much my stomach would be in the way! it was more comfortable for me to bring the bar under my belly, but i don't know that i felt my muscles working as hard doing it that way. i think you have to do whichever is more comfortable for you at this point.
good luck!
carrie