A harvesting machine includes a harvesting header with a header frame, a flexible cutterbar assembly attached to the header frame along the length thereof and configured to cut a crop, and a flexible draper assembly positioned behind the cutterbar assembly to permit the draper assembly to flex with the cutterbar assembly and operable to receive severed crop material from the cutterbar assembly. The draper assembly includes fore-and-aft extending rollers and an endless flexible belt entrained around the rollers. The draper assembly further includes at least one support panel to support the belt.