Yes the pen is tall and the opening narrow, too narrow to my taste. I am waiting to finish a shoe-shaped MB BB bottle (must remain about 0.5ml) to transfer ESSRI to it.
BTW, this is an old MB BB bottle. I'm down to the last drop. And no precipitate yet. That has most often been my experience with other permanent inks, so I am not generally wary of precipitates. I do keep all my inks normally in a closet or drawer, with no exposure to light, tightly closed.
With IG ESSRI what can make a precipitate (as I understand, and I may be wrong) is exposure to O2. So, the smaller the exposed surface, the better. I guess that is why these bottles are tall and narrow, and if so, unused ink would be better in its bottle. OTOH, some plastics do also "breathe" and may let gas exchanges take place, but I do not know which plastic ESSRI uses.
For old bottles, I sometimes take a pinpoint of silicon grease on a finger and rub it against the bottle lip before closing. I know, I could contaminate the ink, but have never had an issue, and besides, I try to never topple them.