I have a pair of 11x2 inch backing plates but am hesitant to build them. I think that rock auto has/had the rear drums for 11x2. As my grandpa used to say "if you don't learn something new everyday then you ain't paying attention ". Glad you are taking time to look/see/ evaluate the concern. Good luck. There is a spec that will help you identify the backing plates. I think I have it. I will take a picture/post the measurements.