Honda's variable stroke length engine

[MECXIC]

The MECXIC animation does show a bit too much crap - the combined inlet/exhaust valve was to have been solenoid operated, and the laser ignition (!) was a bit ongue-ion-cheek too.
Main points are the variable stroke giving extended power stroke with increased torque due to larger crank "throw" during it, with exhaust gas dumping by uncovering of 2-stroke like exhaust ports at the bottom of the power stroke, then and almost 100 purging on the elongated exhaust stroke.
I have a non-running prototype built from a 5hp Honda engine currently, and need to burn some midnight oil getting it to work.
My calculations come out at +20% more energy extracted with a 50% over stroke (very similar to Honda's calculations in fact)........ maybe we are both wrong !
Thanks for your comments guys - I will answer specific questions where I can.