On our website, we have the following recommendations for the size and count of your Edge Tamers:
Tractor to 18-24 hp: two 3″ units
Tractor to 24-30 hp: two 4″ units
Tractor to 30-38 hp: three 4″ units
Skid steers with single cutting edges: four 4″ units
But those are really rules of thumb. We based it on the size/weight of the tractor rather than the width of the bucket, because you could have a 5' or 6' bucket on all sorts of different weights of tractors and run them in all sorts of conditions (flat stone, big crown, asphalt, etc). This thread is for current owners to post the number & size of Edge Tamers you have, what tractor and width of bucket you use them on, and what conditions you use them in. That way members can help each other make a call on what is best suited for their situation.