Dave, My corsair shown on this thread weighs 20 pounds 4 oz with a 91 inch span and it is powered with the older 7-70. The newer 7-77 should give 10% more power. Mine swings a Xoar 22x10 3 blade well. The plane flies fine at 1/2 throttle. Actually I usually take off at less than 3/4 throttle. Be mindfull always with weight while building. No glue glops, less epoxy more CA. Recall these engines have low vibration so the airframe does not have to withstand massive vibration from a single. -Tom