A guy at my field had the Edge 540......had a Saito 100 or .91 on it......he thought he had it balanced, (with additional weight), but after flying, it was noticably tail heavy.....so he zip-tied a pair of pliers to the firewall to add more weight......It was balanced better, but didn't have very good performance....I think it was just too heavy with all the weight. A guy that flies 33-40% scale aerobats flew it and said he thought the plane felt sluggish and heavy. My Extra must have been AT LEAST a pound lighter than his Edge.