A high deflection capping system has an elastomeric sealing member with a sealing lip that, when viewed in cross section, forms a smiling-shaped seal against an inkjet printhead to provide improved printhead sealing, particularly when sealing over surface irregularities on the printhead. This high deflection sealing member may be onsert molded onto a support frame. A series of these sealing lips being molded on a single flexible frame to simultaneously seal several adjacent inkjet printheads, with the flexible frame having a border region with one or more cap bases attached to the frame by plural suspension spring elements. The suspension spring elements have both cantilever and torsional characteristics which allow the bases to tilt and twist independent of one another to seal each printhead. Alternatively, the support frame may be designed to support only a single high deflection sealing member. A venting system is also provided with vapor diffusion handling capabilities.