I think the airplane out there with the biggest gap between max empty weight and as built weight might be the Sandlin Bloop. As designed with a 25hp paramotor engine it tops the scales at 210 lbs. that vittorazi moster 185 weighs 35-40 lbs per manufacturer website, not sure about weight of the 1.3m prop. If you subtract that weight, you have 175 lbs sans engine, leaving 79 lbs of power plant to play with. With, say, a Hirth F23 hanging out getting back, you should be able to tug up some 103 gliders up I would think. Thoughts?