The Sea Wasp (Ryk E. Spoor)

Low-G will help of course, and I'm assuming that their are other tricks to help with the power-to-weight problems (given the head-ware, one assumes that some degree of cyber can be included in the biomorphs, which means you could do tricks like skeletal and muscle reinforcement, both to get the power up, but also to drop the weight), however the major problem is still just the physical arrangement of the human body.

Note that birds don't fly upright, and large birds spend a lot of time gliding. Humans also don't have a keel to attach things to.

Don't get me wrong, I'm a huge fan of people with wings, however for your cinematic effect, with them flying around without a lot of flapping, and being able to hover in place with the wings slowly moving (instead of going at hummingbird speeds, and sounding like a helicopter), you're looking at magic, psi, or super-science. :) The setting for this story hasn't, as yet, shown any of those.

-- Brett, who yes, does spend more brain-time then he should on things like this. :)