It really depends on what you're trying to achieve with the car. Running anything larger than a 20x10" on the F10 is honestly just for bragging rights, as their is zero added benefit from going with a 10.5" or 11" rear. The only thing you'll gain, is added weight, which is a negative.
You're limited by your rear tire selection, and a 20x10" fits any tire you could want to run in the rear if you plan to stay within the maximum tire widths recommended for an F10.
If you have a serious need to add rear traction, a different selection of tires, or a wider tire can help, but on this platform, adding a massive rear tire and a massive rear wheel does nothing but hurt the overall feel of the car with an unnecessary stagger and added rotational weight.
Again, it depends on the overall goal you're going for, but to increase the wheel size, and still keep the car feeling quick on it's feet and increase the vehicles responsiveness and overall dynamics, go for a light wheel in a 20x9" & 20x10" set-up. That's what we run on F10's, and have had nothing but great feedback so far. A 20x10.5" is fine in the rear too.
Hope this helps!
Here's one of our 20x9" & 20x10" set-ups on an F10, running a 285/30/20 out back:
- Andy