Bradley Perrett from Aviation Week writes that the description of Long March 7 corresponds with the mid-sized launcher that the China Academy of Launch Vehicle Technology detailed in 2007. The configuration displayed then had the two K3 core modules, four K2 boosters and a special 3-meter-dia. module, H3, that would presumably be an optional third stage for missions beyond low Earth orbit. But the range of payloads quoted for Long March 7, 10-20 tons, shows that it would be built with a variety of booster combinations. A single YF-100 would presumably provide second-stage propulsion.