So what's the difference between the ST-710 and the ST-770? Is the later just an update of the now out-of-production ST-710. If so, why the different designation?

Also, in this photo, the exhaust tubes are facing forward compared with other photos of the ST770. What's up with that? Are they movable? I assume that the exhaust can just be vented into the air (with a WWI style cowl) as on the original rotary engines.