Iowie, thanks for the feedback and I'm glad you find it useful! Indeed I've noticed the short flip mistakenly treated as long flip problem too, but not very often so I thought maybe it was a mistake of my hand. But since you are reporting this problem too, I'll try to see if it's really a bug.
As for the skipping over problem, I intend the algorithm to skip margins only. For example when you are already reading a page portion just above the bottom margin and hit the flipbar, it should go to the next page (or column) instead of showing the margin. But there is no way to know the width or height of the margin for a PDF file, so I arbitarily set a rule it will skip if the next or previous screen to the edge of the page is less than 1/3 screen. You may need to re-adjust when you find it skipped real text that shouldn't be skipped.