My 4th gen is going to have to reside outside for a couple months and 1) the car has a roof leak problem that will not be resolved in time for it to go outside, and 2) where the car is going to reside is not at my house so i can't watch out for bird poop/sap/other **** daily and the place is a frickin tornado/hail/storm magnet and i want to keep pine needles and twigs and pinecones and stuff from it. And I will continue to use the cover inside the garage once I get it back in the garage.

Based on your question, it’s apparent you’ve done no shopping on your own.

The answer is an emphatic ... yes ... custom fit covers exist.

Looks like Covercraft has options.

I've been using thier weather shield cover (different vehicle) for 6-7 months and I'm happy with it. I've never tied it down on the car either. The fit is that snug.

I've been using California Car Covers. They even ask if you have a OEM spoiler or not, that's how good they fit. And if you had a custom tall spoiler, they can even accommodate you if you let them know up front. I had mine made a few inches lower so that it would cover the Stillen ground effects. Overall, they fit great and do their job.