If your boat is a model with curvature to the hull or pronounced channels, which is the case in boats, you won’t have a secure mount with suction cups. In that case you need our velcro version. Both our standard and XL model come with a 1”, 2” shim or use them both together to create a 3” shim that will help make even the most defined chime fit flush. Still an easy to use system - put the layer of velcro on both the port and starboard while the boat is dry and out of water - and the wakesurf shaper has the corresponding velcro to give a super secure fit.