All you need is to have a solid 3x3 column 2 blocks over the floor. This ball has a good spot on it, the lower ball at the refinery:
There under the northeast corner there’s a 2x2 exposed at exactly head height so if you walk under it, it’s 3x3 as high as you can swing.
11 swings of the hammer for 99 blocks. Since you can only hit up for 11 blocks it’s easy to build a spot into almost any gleam ball, but it can shorten what’s available if you want top-mining on the same ball.
It does cost more bombs as noted but there is zero dealing with weird effects of regen so a little more relaxed on the timing. I’ve found that a top-down farm is pretty stable for about two plots (16 deep) but if you can find a spot for a full three plots in a gleam ball, you’re way under the center of the regen and it tends to push you more to the side.
I found a tree that could do it once but it kicked me out the side nearly every time, and on a gleam ball besides hitting the floor every run (I end up doing this no matter the height) it means you need a larger slide/guide at the top as you’re more likely to arrive off center. And that adds to the tool waste as well as causing some fall damage even if the guide is flat on the ball.
Of course all you have to do is slow down a bit to avoid that but 
Lately I’ve been watching some old re-runs on Freevee (prime channel). They added some old series I liked. It was great to re-watch Fringe completely. But yeah that’s often when I’m farming gleam or trunk, as well.