Piper Cub PA 18 "Super Cub"
This Cub you can fly with engines ranging from Zenoah ZG20 to Zenoah ZG62SL
With the smallest engine, you'll fly scalelike for hours on a pint of gas, with the largest one you'll easily tow gliders weighing 15-20 kg.
There is also room for a ZG62 on Hydromount:
Scale 1: 3,85
Wingespan: 280 cm
Wingearea: 114 dm2
Wing loading: 70-88 g/dm2
Length: 180 cm
Weight: 8-10 kg depending on equipment