On my pens I just fill it all the way ... no air ,,, and write away. The only leaks I've had ... on chinese oens came from the imperfect seal around the nib unit, Those pens had a cellophane seal on both sides of the inner nib unit inside the housing ... I cleaned and dried them then used some nail polish to re-seal. Ive never had a problem since. This happened on one Junhao x-450 and one other. The beauty of those pens is you can switch the nibs out for better nibs. I'm currently using an x-450 with a Sengbusch 17 nib. Its as close as I'll ever get to the Mont Blanc Calligraphy pen and only cost $3.00. My x-750 all came with architect/hebrew nibs which is the grind I prefer. My other current pen is an older Pelican M-200 with semi-flex nib ... since replacing the broken piston I fill it as an eyedropper. I switched my hobby from pens to pipes so I am a bit out of touch on the pen hobby.
My Jinhao Dragon pen is one of the best fountain pen surprises, it's only an ordinary medium nib but it was almost as excellent as my best tuned nibs right out of the box (I'm sure there is some element of luck there but it proves the point as well as anything, the price of the pen rarely impacts the writing quality).
I have a 159 with a swapped nib somewhere, but I seem to remember having carved out the feed to try and keep up with a 1.5mm stub and it drools a bit now.
... However, it's hard to beat a rollerball for trouble-free performance in any environment in this case the Uniball 207 is my weapon of choice.
History certainly twists and turns.
Throughout college I searched the stationary stores for any pen that could write consistently, I was even willing to buy the fancy pressurized Fisher Space Pen cartridges but those turn out to have a short shelf life and even less consistency than your average ballpoint.
Every few months I would take my desk mug full of "failed" ballpoint pens and in a righteous anger snap them in half one by one.
I spent at least one entire year of college using nothing but fine tip felt pens because ball point pens are so infuriating.
Naturally I did eventually find the famous Pilot G2 (the only ballpoint pen I have ever been satisfied with), but guess what else Pilot is famous for?
This isn't the pen that started my FP addiction but it is my #1 favorite pen ever since I held it.
The Custom 742 in Music nib, the best behaved stub nib you'll ever find, wet but never drooling, and the barrel houses the Pilot Con-70, a capacious 1ml cartridge/converter with a vacuum pump filler (I can't say I prefer it to a piston type but the large capacity more than compensates).
This pen writes so well it convinced me to give up on chasing flex nibs forever.
(None of the modern flex nibs write like a proper wet noodle and vintage pens inevitably come with their own gremlins.)