I've seen a few fireballs make it up there quickly, although I didn't happen to notice the bonus timer value. Unlike Dan, I don't think I've ever seen one make a beeline to the top; there's usually some back and forth movement on at least one of the girders. While running boards, I've had plenty of fireballs get to the 6th girder ahead of me, escaping via one of the two ladders while I was giving chase with the top hammer. That's really not uncommon, as I don't consider "running boards" and "top hammer" mutually exclusive. In those types of games, it's also not rare to experience difficulty just "getting to" the upper hammer, courtesy of a rapidly climbing fireball.
I had one game recently, on a Level 5+ barrels board, where the fireball ascended the middle ladder almost immediately. I decided to let it go, and waited until I felt a decent bottom hammer was likely. Before the hammer had expired, I noticed that the fireball was already on the 6th girder. Since I was busy steering and smashing barrels, I wasn't aware of what path it took to get there.
Bottom hammer timing is a debatable DK topic. When the initial fireball decides to be an early climber (middle ladder to the 2nd girder), you have a couple of choices. You can grab the hammer right away, and try to smash the fireball before it has a chance to create havoc later in the stage. Or, you can wait, in hopes of setting up a huge bottom hammer. Murphy's Law dictates that 70% of the time, whichever option you take will be the wrong one.
