Thanks StefanP: I've gone back into MotoCalc and switched to 2000 mah SR cells and reduced the number to 18. Total weight of pack is now 37.20 oz. Hacker B50-15L = 8.81 oz. ESC = 1.5 oz., so total drive system is approx 48 oz. I plan on using mini servos as well. I've calculated the thrust to be 50.8 oz for a T/W ratio of .55:1. Wing loading at conservatively projected airframe weight of 48 oz is now 32.2 oz/sq. ft. Unfortunately, my Watt meter is back in the States on my buddy's workbench. I'll be extra careful with my balsa selection and avoid ply wherever possible. Thanks, Thom