A plastic bottle base is formed with a seating ring perpendicular to the axis for supporting the bottle on any underlying surface prior to hot filling. An inner portion within the seating ring extends upward and inward toward a center bottom wall surrounding the axis. A flexible diaphragm portion extends outward from the seating ring to join a heel portion at a substantially horizontal inflection point. The diaphragm portion is sufficiently flexible to respond to changes in bottle volume and vacuum to allow the seating ring to move upward so that the seating ring is above the heel portion of the bottle. This flexible base is combined with a sidewall defined by a small number of barrel shaped surfaces separated by indented ring segments to form a panelless plastic bottle capable of hot-filling and capping. The sidewall geometry is configured such that the plastic bottle prior to hot filling can be a lighter weight and/or can have a reduced number of indented ring segments, while having a satisfactory vacuum resistance to localized paneling and/or ovalization.
