[Oztrich Boy]

For example, the heavy tail of dinosaurs (needed for balance on two legs) would prohibit any possible flight. And besides, the theropods were "lizard-hipped" dinosaurs, not "bird-hipped" as would be expected for bird ancestors.

Creatinoid Hand waving

It's not "and besides". "Bird hipped dinosaurs" and birds developed "bird-hips" (actually a rearward pointing pubis bone) for the same reason: to tuck the digestive system into the pelvis and move the Centre of Gravity aft.

Without that, a vegetarian dino has to be quadripedal. With their smaller gut, carnivorous dinos don't need that, but they do need to get rid of the tail for efficient flying. Not only the weight, but a long reptile tail prevents stall-landings.

Parallel evolution: Form follows function, same as dolphins and ichthyosaurs

[curiosity]

I have a science question: why were carnivorous dinosaurs bipedal? What advantage does that provide?