Here all the forces in the crank mechanism ... Reduction in the stroke of the shaft twice reducing, with the same stroke of the piston causes a large increase in efficiency, by reducing the forces of inertia. Also the force Nm sometimes reaches up to 30% of gas force , which can be seen in the charts.
http://www.new4stroke.com/sily%20w%20cylindrze.pdf
When it does not exist at all, the average efficiency of these 10 to 15% of the engine will be higher. only because of its lack ..
Adding a fall in the shaft stroke by 50% from the inertia forces, even the next 10% increase in efficiency will be able to achieve ... in total, some 25% efficiency will be better ...
Andrew