can773 is spot on target -
A heavy model is of NO use ---in a powered model -
In a speed glider -yes - as it uses inertia to gain speed in dives.
A powered aerobat simply can NOT be built too lighty- Too flimsy and a poor aerobatic setup - - yes
- but if power loading is extreme and weight loading is extremely low - you have the best possible setup.
Windy weather flying - (20mph) with this type setup looks far smoother as speed can be varied as desired.
Been there dun it -as have many others --
Building really light with lots of power takes more work -