I've read most of this stuff before and I can't find any evidence to support Biddle's assertion that the panel found hitting on the edge grain is "very likely a big part of the problem" (with breaking maple bats). I tend to think it's a very minor part of the problem. Everything I've read concludes that the most significant factor by far was/is grain run-out (slope of grain). That's why you rarely see broken MLB bats that look like sharp weapons these days, the manufacturers are making bats from billets with much straighter grain. And also why a high quality bat will usually outlast a cheap one (grain not straight) by a lot.
I'm still not completely sold that hitting on the face grain makes much, if any, difference on breakage. The science is solid that a maple bat handle is stronger on the face grain than on its edge grain (which is the origin of the label recommendation). However, that only measures dropping a weight on the end of the handle until it breaks. That doesn't really account for what happens to a handle when the ball is hit hard off the end of the barrel. That's a different kind of stress on the handle (see picture where ball is hit on the face grain). The difference in strength between edge/face is completely different with ash. So I'll continue to believe that it really doesn't matter with maple, but I do acknowledge MLB recommends hitting maple on the face grain for safety purposes.
But what I'd really like to see is a study comparing ball exit speeds from the two sides. (A project for the new group at Driveline Hitting?) Most guys would give up a little durability for more pop.
More references:
http://www.rockbats.com/techNotes/RB-TN-F.pdf