215 would work for a 7" wheel. In regards to GRM, i.e. Grass roots motorsports magazine, they don't publish all of their articles online, the testing I believe was in last months copy.
If I remember correctly, a lot of the tire to rim sizing really had to do with how the tire felt. When it was matched correctly, the tire felt very responsive, and turned in well. This in turn improved on tester confidence and led to the faster times on the test course.
Parking Lot Hero
2008 WRX daily driver
2003 ZX3 23D Autox Car 42 FSP
"Hella Functional - Raced, Not Hard Parked"