The 215 on the 15x7 would probably be into your fenders. You can see that the backspace between the 15x6 and 15x7 is only different by .1". That means the rest of the .9" of additional width is to the outside on the 15x7". It also means the centerline of the wheel has moved.
The easiest way to see that is with an offset spec. The 15x6" has an offset spec of about +3. The 15x7 has an offset spec of -7. So the centerline of the wheel moved out toward the fender ~10mm between the two. That's why the 215 should work on the 15x6, but the 205 is the best you can do on the 15x7. You'd need a 4-3/16" backspace on the 15x7 for the centerline of the wheel to be in the same place as the 15x6.