Bear in mind that each dash in the coupler curve represents 5 degrees of input crank motion (as does each gap). Also, when the coupler point reaches a cusp, its motion stops for an instant.
Keep a log of each link combination you have tried. When you arrive at a final design, print it from the web atlas. Input the mechanism parameters into a software package such as Fourbar and print out the mechanism and coupler curve in order to confirm its shape.
Department of Engineering at Cedarville University