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It should be pointed out that the graphical three position synthesis is usually applicable only for one link in a mechanism consisting of revolute joints. But since our requirement is to have one mechanism replicating the motion of three links, we decided to independently carry out three-position synthesis for these links and merge them on to the same mechanism. The links are assigned measurements 2.5in, 4in and 3in for the top, middle and bottom links respectively. The three position synthesis for the rear leg is shown in the figure below (shown along with construction lines). The corresponding AutoCad file is also attached (?rear-new-differentlengths.dwg). 
The links are denoted by the lines displayed in red and the dark circles indicate the ground locations. Autocad Force Effect Motion software available as an application on iPad is used to simulate the mechanism. The photo attached below displays how the mechanism for the rear leg looks within that application.
The links BC, CE and EG are the required links for the rear leg and A, F and D are the grounded points. The trajectory mapped by the joints B,C, D and E are shown in blue. The arrows along the trajectory indicate the respective joints' velocity and acceleration. Similarly, the position synthesis of the front leg can be found below (shown along with construction lines) and the corresponding AutoCad file here ( front-differentlengths-twopos.dwg ).
Based on a careful analysis of the front leg in the video, we felt that the links attached to the leg do not make complex motion and decided to adopt the first and last position for synthesis. This simplification led to us using the Graphical Two-position Synthesis technique.
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