Yes! It will be worth it.
To achieve the optimal effect it is best to stay with the Template no matter where you cut it off.
The 22° limit is not EVER intended to be looked at until you are like 5 feet back behind your car. That is the gross absolute limit the air will remain optimally attached PROVIDED you have followed the template to that point. If you dive down to 22° when you should be at only 8°. it will not be a good thing.
Think of it like this, the front of you car has lifted the air up and out of the way, it now wants to drop back down to where it started, and the more gently you can let it slide down the back of your car, for as long as possible with the template as a guide, this will achieve the best result. If you drop the angle too abruptly, the air will not follow the shape of your car, and the pressure will drop too much.
So, That said, I think it OK to cheat it down a little bit for a short Kamm like you have, this is only based on what I see with the Honda Fit & Toyota Prius. It kinda make sense to minimize the wake size as opposed to following the template and having the highest pressure return.
Use my post #6 if you want to optimize the design, drastic angle changes will unhinge some of the benefit you are seeking to gain. Besides, I'm asking you to keep it higher which has the added benefit of improved visibility in addition to cracking good aero performance.
Tuft testing only tells you if you really screwed up, air will be attached with your current design, and certainly with my proposal. Tuft tests also only show what the air is doing in the 1/4 inch layer of air on the car, the air being moved about drastically by your vehicle goes out several feet, and the air being affected in total is out to several yards. It is hugely complicated how it all interacts to the point where even with supercomputers and teams of engineers, we still build multi million dollar wind tunnels to test things in real life.
We're really talking about optimization here, not whether it "Works". Clearly your MPG results show what you have currently offers some improvement, raising it, going to an easier transition, will only improve it that much more. In my opinion.
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