Aeromodding is like hotrodding, if you want it done better you got to do it yourself. Going from a Subbie to a 2 wheel drive vehicle will get you at least 10% just from reducing driveline losses.
The Subbie could be a fun aeromod project, I considered it along with other vehicle bases. But the complications of dealing with transaxle also applies to 4 wheel drive vehicles and that eliminated it from my considerations. It's not impossible, but it wasn't what I was looking for in a vehicle. If you want to try something radical with your Subbie we'd love it if you shared the project with us
. I've seen a RWD conversion on a Subbie, it wasn't worth the few hours it took to make the front driveline vestigial. If you keep the car keep the 4 wheel drive, it's worth it
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BTW, when comparing how much power it takes to move a car; 1% is an improvement, 3% is worth some risk, 5% is a good investment, at 10% you're a fool if you don't do it. 30% is huge even if the biggest difference is the small frontal area. Do what you can with what you got, it'll go farther.