Learned this technique awhile ago. Its a modified version of certain SWAT teams CQC pistol techniques. I've tried it a few times at the range, at 10 yards its effective, and is really stable. The downside is it limits vision directly infront and down of you, so flat spaces its fine but stairs and cluttered walk spaces can make it difficult to move learned that the hard way when I was trying it out dry fireing practicing with it. It really forces you to maintain focus on the front sight. It also makes switching hands easier, or off hand shooting easier.