The Latest new and Improved Hoist from Fredlin - Designed for Lifting roof top tents off vehicles. 
 
The Mounts on this tent hoist fix into Timber / concrete or steel - with pre cut 10mm wide / 50mm long slots positioned along the beams to maximise mounting opportunities. Slots are pre cut into the steel positioned as follows;
(From end - 40mm and 300mm coming to a slot in the middle  at 800mm (Middle) .
If the bolt holes don't line up with structure in your roof - it would be easy to drill new holes in the position you require. See Diagrams in the picture for full details. 
 
The Quality of the mechanism looks excellent, and the manual winding saves messing around with floor mounted electric winches. Simple and effective.