A new class of viscoelastic constitutive equations is proposed that provides enhanced control of shear and elongational properties. Together with the widely used Giesekus and Phan-Thien Tanner model, these enhanced models are evaluated for a polymer melt (LDPE) in a cross-slot flow. This stagnation flow has a strong planar elongational deformation component. The material is characterized, in both viscometric simple shear flow and in uniaxial elongation. Velocities are measured with particle tracking velocimetry while field-wise flow-induced birefringence is used for correlation with stresses. The experimental results are compared with 2D viscoelastic simulations. With equal quality of describing viscometric data, the enhanced models can predict the flow properties of the cross-slot flow significantly better than the well known PTT and Giesekus model.