You will have to deal with the insane thermal flux too. Even where the atmosphere is Earth-like in temperature, you will have a very hot radiator below you and

You will have to deal with the insane thermal flux too. Even where the atmosphere is Earth-like in temperature, you will have a very hot radiator below you and frozen space above. (If you were in low Venus orbit, and could "stick your head out" of the spacecraft, Venus would feel as warm on your face as the noon sun on Earth. On the night side. That's how hot the planet is.) So for anything larger than algae, even in the convective atmosphere, you're going to have a side that's burning hot and a side that's freezing.