VTOLs can't use Superchargers. They can mount VTOL Jet Boosters. The VTOL Jet Boosters also double the VTOL's Cruising MP so if you want a max of 18 MP, you want an engine capable of 9/14[18]. You could also factor in Overdrive too, if you want. That would lower the engine to 7/11[14/18] and free up more tonnage.
Also since lift hoists aren't that well defined, the Doublehead could utilize two cables as part of a single Lift Hoist. That would fit with the 24 tons empty, 48 tons loaded.