[elhigh]

50+ in an auto-equipped Corolla might be as good as it gets. I'm struggling to do that well with a hybrid.

You're beating the EPA highway rating by 50% or more and coming from a bigger engine, more weight, a larger body and a worse transmission for it. You could take the belly pan further aft and consider full skirts on the rear wheels at least, but these are excellent results already.

I've been getting hammered by extensive AC use; I'm thinking the next step is to add ceramic window tint to keep the interior cooler and take some load off the engine that way. That's worth considering.