With the Model S LR, you can consider doing 20x9.5 square with 255/40/20 or 265/40/20. We have done few testing on the S LR with 265 square and the 1/4 miles run are exactly the same as factroy setup.
Not only you are getting the same performance as the factroy setup, you will also get a better effieiecny, lower cost on tire ,and longer lasting thread since you can do rotation.
As far as fitment, you can skip the spacer and go with rear adjustable camber arm. You are able to achieve the same flushness front and rear once you bring back the rear camber to around -0.5 degree.
Example of the 20" square setup we did:
View attachment 955424
View attachment 955425