I did some research on Jumping, albeit not a great deal. I did try a FLAT tip & it was accurate as any tip I'd ever tried. But sometimes, there is a need to hit off center, for a Jump-Masse, so a flat tip is OUT...
In the engineering business, a round end is said to be a crown. The dimension from an imaginary line (outside corner to outside corner) to the tangent of the round, is said to be the crown height. I think my Predator Jump Cue is about 0.040 in height. Works for me... You can read about Break Cues in my book, titled, "The GREAT Break Shot". It's 180 pages.
The crown diameter on my Break Cue is larger than a 50 cent coin.... it has a small crown height, maybe 0.025 of an inch. It has been a long time since I used my Break Cue, as I only play Golf on a Snooker Table anymore. I just turned 77.