There are a lot of things that go into getting those things off the ground. Clearly, thrust to weight is one, but one has to look at what the wing loading is, and how drag fits into it. Not to be obvious, but to make a not too subtle point, what is the thrust to weight ratio for a glider? But beyond that, one could have a decent TTW ratio at .70; i.e. 24oz thrust to 34 oz acft.