You would most certainly notice the loading difference between the ZDZ and Zenoah. I few this particular plane in a few different variations and in each case the lighter one flew better than the heavier one. When the Sig Sukhoi was designed there was not as much attention paid to airfoils as there is now so the wing planform is not as good as it could have been. It actually flys best with a lightest engine that has the power to fly it.