I'm going to say more than I really know about this subject and ask that if I make mistakes others who are more knowledgeable please correct me.
"Reverse flare" is a confusing term, it implies that something drastic occurs and the flare "flips". Actually, the direction of flare in the area we are concerned about - the track area beside the thumb and finger holes - is determined by the location of the bowties (yes, there are two, one on each side of the track). The location of the bowtie nearest to the area of interest can be APPROXIMATED by drawing a line from the PAP through the pin to the first flare line. In most layouts, this bowtie is located above and to the left of the finger holes (I will refer to tracks for right handers). With the bowtie in this location, the track flare is away from both the thumb and fingers. The layouts for some of the Hammer balls have a good graphic of this. But if the pin is lowered far enough, the bowtie moves to below the fingers and the flare is now away from the thumb hole but toward the finger holes. For a high 3/4 track, this type layout may clip the finger holes on the later flare rings. And if the pin position is lowered even further, to positions well below the grip mid line, the bowtie is lowered so far (to a position below the thumb hole) that the flare is now toward both the finger and thumb holes. This is what is referred to as "reverse flare". Note that the flare has not actually reversed IN RELATION TO THE PIN AND PAP, which is the determining factor, but only in relation to the grip. The lower pin positions are often referred to as full roller layouts, since for a full roller they flare away from the thumb and finger holes (still flaring in the same direction as determined by the pin, but away from the holes because of the track position). But these layouts, with care, can also be used for low track 3/4 players. This is how I understand "reverse flare". -- JohnP
As a humorous aside, I spell checked this and Word insists that bowtie should actually be "bootie".