Several years ago I did a bunch of pattern tests with 6's and 5's. I found that the blend gave me a pattern that was worse that just 6's or just 5's. I suspect the same is true of 7.5's and 8's. I've come to believe that one of the most important factors in getting a good pattern is the consistency of shot size. The more variance you have in shot size, the more flyers you're going to have. The only exception to this is the "complex" loads that have all the 6's on the bottom and the 5's on top. Those seem to pattern pretty well. But when you mix shot sizes, like you'd find in reclaimed shot, you can't get a decent pattern from it.