I don't think many 3d planes have 3:1 thrust to weight. 2:1 is lots and I find 1.5 is a little too little. 3:1 is a Hacker A20 on a 10oz foamie, a Saito 100 on a 4 lb Mojo. At some point it gets silly. What would you power a 30lb 40% plane with if you NEED 3:1?